JP2004160700A - Simulation apparatus for injection molding process and method for estimating shape precision - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simulation apparatus for an injection molding process capable of supporting the optimum setting of the mold design, molding condition or the like of a plastic molded product. <P>SOLUTION: The simulation apparatus for the injection molding process includes a heat transfer analyzing means for performing the heat transfer analysis of a mold and a molded product, a flow analyzing means for performing the hot fluid analysis of the filling/dwelling/cooling behavior of the molten resin in the mold and a structure analyzing means for performing the structural analysis of the molded product and the mold and estimates the shape precision of the molded product. This simulation apparatus is also equipped with a pressure/temperature calculating means for performing the heat transfer analysis of the mold and the molded product and the hot fluid analysis of the molded product individually or simultaneously to calculate the temperature of the mold, and the pressure and temperature of the molded product. The structure analyzing means sets the calculated pressure and temperature as an initial value to consider the mold and the molded product at the same time and performs structural analysis considering the mold restriction of the mold with the molded product and the viscoelastic characteristics of a resin to calculate the shape precision of the molded product deformed by thermal shrinkage. <P>COPYRIGHT: (C)2004,JPO

Description

ここで、Ｇ∞：平衡弾性率、ｔ’：緩和時間、λｎ
：緩和時間係数である。
【００４０】
ｌｏｇ１０ＡＴ （Ｔ）＝Ｃ０ ＋Ｃ１ ・Ｔ＋Ｃ２・Ｔ２ ＋Ｃ３ ・Ｔ３ ＋Ｃ４ ・Ｔ４＋・・・・・＋Ｃｎ ・Ｔｎ…… （２）
ここで、ｌｏｇ１０ＡＴ （Ｔ）：温度シフトファクタ、Ｃｎ ：係数、Ｔ：温度である。
【００４１】
ここで、ステップＳ２３における粘弾性を考慮した構造解析を実施する際、成形品である樹脂の温度挙動は、流動時には金型壁面近傍が固化状態であるが、成形品の内部は溶融状態にあり、この２つの相が混在した状態で徐々に冷却固化していく。従って、樹脂の粘弾性マスターカーブは固化状態のみならず溶融状態の両方が必要である。よって、固化状態から溶融状態の全域に亘って１つの粘弾性マスターカーブを作成して利用できると溶融状態での粘弾性特性も正確に考慮され、非常に効率的で有効である。
【００４２】
そこで、ステップＳ２３における粘弾性を考慮した構造解析で用いる粘弾性物性値を求める方法についてポリオレフィン系樹脂の場合を一例として詳しく述べる。
【００４３】
粘弾性試験方法としては、樹脂が固体領域において矩形型試験片（厚さ２．５ｍｍ、幅１２ｍｍ、長さ４０ｍｍ）を用いる強制捩り法（角周波数掃引）並びに樹脂溶融時、円錐／円板治具の間に挿入する円板試験片（厚さ２．５ｍｍ、直径２５ｍｍ）を用いるせん断法（角周波数掃引）を適用した。
【００４４】
図３は矩形型試験片を用いる強制捩じり法による動的粘弾性の測定装置の概略を示す図である。
【００４５】
この方法は、試験片下端が振動モータに、上端がトルク検出用トランスデューサに連結されており、矩形型試験片の両端をチャックで固定した後、その一端を固定した状態で他端に角周波数の正弦的な捩り変位を印加する。このときに発生するトルクを測定する粘弾性測定法である。
【００４６】
矩形型試験片の厚さ、幅、チャック間距離から試験片に発生する捩り歪み振幅が求められ、試験片が変形する際に弾性的に貯えられたエネルギーに関係する貯蔵弾性率Ｇ’と粘性的に損失したエネルギーに関連する損失弾性率Ｇ”を求めることができる。
【００４７】
図４は円板試験片を用いるせん断法による動的粘弾性の測定装置の概略を示す図である。
【００４８】
この方法は、モータ、トランスデューサにそれぞれ連結した円錐、円板状金属製治具の間に試験片を挿入し、円錐から試料に角周波数、回転振幅の正弦的な変形を印加した時に発生するトルクを測定する方法である。
【００４９】
円板の半径、円錐と円板とのなす角度から歪み振幅が求められ、試験片が変形する際に弾性的に貯えられたエネルギーに関係する貯蔵弾性率Ｇ’と粘性的に損失したエネルギーに関連する損失弾性率Ｇ”を求めることができる。
【００５０】
測定装置としては、レオメトリック社の粘弾性スペクトロメータを使用し、固体領域から溶融遷移領域である２３℃〜１９０℃の温度範囲においては強制捩り法を、溶融遷移領域から溶融領域である１３０℃〜３００℃の温度範囲においてはせん断法により測定を行った。尚、角周波数は０．１〜１００ｒａｄ／ｓ、歪み振幅は０．１〜１０％の範囲で与えた。
【００５１】
図５は固体領域から溶融遷移領域の各温度での捩り法による動的粘弾性測定により得られた貯蔵弾性率Ｇ’の角周波数依存性の測定結果を示すグラフ、図６は固体領域から溶融遷移領域の各温度での捩り法による動的粘弾性測定により得られた損失弾性率Ｇ”の角周波数依存性の測定結果を示すグラフ、図７は溶融遷移領域から溶融領域の各温度でのせん断法による動的粘弾性測定により得られた貯蔵弾性率Ｇ’の角周波数依存性の測定結果を示すグラフ、図８は溶融遷移領域から溶融領域の各温度でのせん断法による動的粘弾性測定により得られた損失弾性率Ｇ”の角周波数依存性の測定結果を示すグラフである。
【００５２】
これらの測定結果より、温度−時間換算則を適用することにより、基準温度（今回の樹脂の場合、固体領域から溶融遷移領域での捩り法においては１３８℃、溶融遷移領域から溶融領域でのせん断法においては１９０℃）に対し、捩じり法とせん断法で得られた各測定温度での貯蔵弾性率Ｇ’と損失弾性率Ｇ”を時間軸上（水平移動）を順次移動させて重ね合わせを行った。これらの結果を捩り法については図９及び図１０に、せん断法については図１１及び図１２に示す。
【００５３】
図９は図５の捩り法による動的粘弾性測定により得られた各温度での貯蔵弾性率Ｇ’をシフトして重ね合わせた後の貯蔵弾性率の周波数依存性を示すグラフである。図１０は図６の捩り法による動的粘弾性測定により得られた各温度での損失弾性率Ｇ”をシフトして重ね合わせた後の損失弾性率の周波数依存性を示すグラフである。図１１は図７のせん断法による動的粘弾性測定により得られた各温度での貯蔵弾性率Ｇ’を重ね合わせた後の貯蔵弾性率の周波数依存性を示すグラフである。図１２は図８のせん断法による動的粘弾性測定により得られた各温度での損失弾性率Ｇ”を重ね合わせた後の損失弾性率の周波数依存性を示すグラフである。
【００５４】
以上の図に示してきたように、各測定温度での貯蔵弾性率Ｇ’と損失弾性率Ｇ”は、基準温度に対して全て重ね合わせが可能であることが分かる。これは、樹脂が温度−時間換算則が成り立つ熱レオロジー的に単純な材料であることを示している。この基準温度上に全て重ね合わせられた貯蔵弾性率Ｇ’と損失弾性率Ｇ”の曲線をマスターカーブと呼ぶ。図１３は捩り法における重ね合わせ時の各曲線の移動量を移動因子（シフトファクタ）として表したグラフである。図１４はせん断法における重ね合わせ時の各曲線の移動量を移動因子（シフトファクタ）として表したグラフである。
【００５５】
次に、上記捩り法、せん断法の両者で得られた貯蔵弾性率Ｇ’と損失弾性率Ｇ”のマスターカーブを更に重ね合わせ、樹脂の固体領域から溶融領域の全ての領域に亘って１本の最終マスターカーブが得られるか否かの検討を行った。図１５はせん断法での結果を捩り法での基準温度１３８℃上に重ね合わせた貯蔵弾性率Ｇ’、損失弾性率Ｇ”の時間依存性に関するマスターカーブを示すグラフである。図１６は図１３及び図１４を更に重ね合わせ時の移動因子（ｌｏｇａＴ
）の温度依存性を示すグラフである。
【００５６】
この結果から、樹脂の固体領域から溶融領域の全ての領域に亘って１本の粘弾性マスターカーブを作成できることが分かる。
【００５７】
尚、最終的に、この貯蔵弾性率Ｇ’と損失弾性率Ｇ”のマスターカーブを線形粘弾性解析で使用できるようにするためには、貯蔵弾性率Ｇ’と損失弾性率Ｇ”から緩和スペクトルへ変換し、これから緩和弾性係数を求めてプロニー級数近似することが必要である。
【００５８】
図１７は図１５から得られた貯蔵弾性率Ｇ’、損失弾性率Ｇ”を変換して数式（１）に示すプロニー級数近似し、温度に対する緩和弾性係数Ｇ（ｔ）の関係を示したグラフである。図１８は図１６から得られた時間−温度移動因子を数式（２）に示す多項式により近似し、両者を比較したグラフである。
【００５９】
以上、成形品部である樹脂の粘弾性特性を動的粘弾性試験法により、固化状態（強制捩り法）と溶融状態（せん断法）についてそれぞれ測定し、両者を重ね合わせることで、プロニー級数（緩和弾性係数）、シフト関数（時間−温度換算則）を用いた１本のマスターカーブを作成でき、線形粘弾性モデルを適用することにより解析可能であることを示した。
【００６０】
本発明においては、樹脂の固化状態で得られる粘弾性マスターカーブのみならず、樹脂の固化状態と溶融状態それぞれで得られる動的粘弾性特性を１つに統合した粘弾性マスターカーブを作成し、この物性値を使用して金型並びにプラスチック成形品形状の熱収縮に伴う変形挙動を求めるための構造解析を行うことを特徴とする。
【００６１】
更に、上記粘弾性物性を考慮した構造解析を実施するのと同時に、冷却固化に伴う成形品表面と金型表面での接触、解離等の型拘束の影響も考慮する。具体的には、ステップ毎の応力解析（ステップＳ２３）が終了した後、成形品表面と金型表面において、両者の接触距離（成形品と金型両者の接触面を構成する要素節点の距離）と、接触面構成節点での反力とにより接触／解離判定を行う（ステップＳ２４）。
【００６２】
接触判定時には、成形品と金型の接触面における熱通過率を設定し、解離判定時には、成形品表面とキャビティ空間の間に熱伝達率を設定して次のステップの温度解析に反映する。
【００６３】
上記非定常温度解析（ステップＳ２２）、粘弾性を考慮した構造解析（ステップＳ２３）、接触／解離判定（ステップＳ２４）の手順を、成形条件として入力された成形品取り出し温度或は取り出し時間になるまで繰り返し（ステップＳ２５）、この条件（温度或は時間）になった時点で、離型処理（成形品が金型による拘束から解放）に伴う成形品のスプリングバック（Ｓｐｒｉｎｇ Ｂａｃｋ）量の計算を実施し（ステップＳ２６）、その後、大気中で自然冷却されて室温に至るまで引き続き粘弾性を考慮した構造解析を行って、最終的に変形量、応力、歪み等の計算結果を出力する（ステップＳ２７）。その後、解析処理を終了する。
【００６４】
［実施例１］
次に、上記解析処理の具体例を示す。
【００６５】
図１９は具体的な成形品形状を示す図である。この成形品形状は、２０ｍｍ×２０ｍｍ（板厚６ｍｍ）のゲート形状を有する、６０ｍｍ×６０ｍｍ（板厚６ｍｍ）の単純な厚肉平板である。全体の解析処理は、図１の手順に従って行う。
【００６６】
図２０は図１９の厚肉平板も含めた金型全体モデルの形状を示す図である。この金型全体モデル１１は左右対称であるので、図２０にはその１／２のモデル部分だけが示されている。この金型全体モデル１１は、固定側金型１１ａ及び可動側金型１１ｂと成形品１１ｃから構成されるモデルである。
【００６７】
図２１は５０００要素に分割された金型全体モデルを示す図である。要素分割プリプロセッサにより、図２１に示すように、金型全体モデルを要素数５０００程度に分割した後、対称面、金型と成形品の材質領域、流入境界等の各種境界条件を定義し、流動解析用の入力データを作成する。尚、流動解析後に実施する拘束条件等の構造解析用の境界条件も併せて付加する。
【００６８】
最初に、流動解析により、樹脂が金型内に充填して保圧冷却される過程を解析する。この解析プログラムとしては、市販されている汎用流体解析ソフトウェアを使用し、これに樹脂の非ニュートン流体としての性質である粘性が温度とせん断速度に依存する関係式、即ち粘性方程式と保圧解析時に必要となる圧力と温度と比容積の関係式であるＰＶＴ状態方程式とをソフトウェアに付属のユーザーサブルーチンを利用して定義する。
【００６９】
又、これと同時に、このユーザーサブルーチンを使用して流動解析のすぐ後に実行する構造解析用入力データを作成するデータ変換プログラムを組み込んでおくことにより、構造解析で使用するための圧力、温度データ、形状入力データが作成されるようにする。
【００７０】
図２２は流動解析で得られた保圧冷却過程が終了した時点（樹脂の流動が停止した時点）の成形品の温度分布を示す図である。図中、濃淡で温度分布は表されており、ゲート側のａ点の温度が最も高く、ｂ点の温度も高く、金型に接する部分のｃ点の温度が最も低くなっている。この場合の温度範囲は１８３℃〜９３℃である。
【００７１】
次に、保圧過程が終了した後の成形品の冷却中の熱収縮挙動を流動解析での温度・圧力の最終結果を初期データとして、構造解析に取り込み、型拘束を考慮した粘弾性解析を行う。
【００７２】
図２３は金型全体モデルの温度分布を示す図である。
【００７３】
図中、濃淡で温度分布は表されており、ゲート側のｄ点の温度が最も高く、ｅ点の温度も高く、金型部分のｆ点の温度が最も低くなっている。尚、この解析では、図２３に示すように、温度解析については金型と成形品の全体について解析を行っているが、粘弾性解析については金型の部分を剛体として解析を行っている。解析入力データは、既に流動解析の実行時に作成されているので、すぐに実行が可能である。
【００７４】
解析プログラムとして、市販されている汎用非線形構造解析プログラムを使用し、樹脂である成形品部については時間−温度換算則が適用可能な熱レオロジー的に単純な材料と考え、前述したプロニー級数（数式（１））による緩和弾性係数の定義が可能な線形粘弾性モデルを用い、シフト関数（数式（２））についてはユーザーサブルーチンを使用して定義することにより解析を行う。
【００７５】
又、冷却固化に伴う成形品表面と金型表面での接触、解離等の型拘束の影響も考慮する。尚、接触判定時には成形品と金型の接触面温度が同じになるように熱通過率を設定し、解離判定時には、成形品表面とキャビティ空間の間が断熱となるように熱伝達率を設定する。
【００７６】
図２４は冷却に伴う樹脂の体積収縮によりキャビティ内で成形品が金型から解離している成形品表面部分（樹脂流入口側）で断熱作用により温度が高く、金型に接している成形品表面部分で温度低下を生じている例を示す図である。図中、濃淡で温度分布は表されており、ゲート側（樹脂流入口側）のｇ点の温度が最も高く、金型に接している表面部分のｈ点の温度が低くなっている。
【００７７】
最終的に成形条件として設定した取り出し時間になった時点で、離型時の成形品のスプリングバック挙動を解析するために、金型による成形品の型拘束の影響を除く処理を行い、その後、大気中で自然冷却されて室温に至るまで解析を行って、最終的な変形量、応力等の結果を得る。
【００７８】
図２５は本解析で得られた金型から成形品を取り出した時点の成形品の変形を示す図である。尚、図中の変形状態を分かり易くするために、表示倍率を大きくした状態で結果を示している。
【００７９】
＜実施の形態２＞
次に、本発明の実施の形態１に係る射出成形プロセスシミュレーション装置について示す。尚、前記実施の形態１と同一の構成要素については同一の符号を付して示す。
【００８０】
本実施の形態に係る射出成形プロセスシミュレーション装置は、前記実施の形態１の図１と同様、基本的に形状を定義して有限要素法等の解析で使用する要素分割を行って解析モデルを作成する形状定義部１、金型と樹脂の伝熱解析を含み、充填保圧冷却過程の解析を行う流動解析部２、及び樹脂のクリープ、応力緩和等の粘弾性的な性質と樹脂冷却時の金型と成形品との間の型拘束を考慮した構造解析を行う構造解析部３を有し、これらの各部の機能により全体の解析処理を行う。
【００８１】
先ず、形状定義及びメッシュ分割を行う（ステップＳ１）。このステップＳ１の処理では、ＣＡＤシステム等により、解析対象となる金型と成形品の形状を定義した後、有限要素法等を用いた要素分割プリプロセッサで要素分割を行い、解析モデルを作成する。尚、必要に応じて、ＣＡＤインターフェースを利用して形状を取り込む。
【００８２】
本実施の形態の解析では、流動解析に引き続いて構造解析を行うので、形状定義及びメッシュ分割を行う際、予め拘束条件等の構造解析用の境界条件を付加しておく。
【００８３】
その後、解析を行うための成形条件（射出速度、樹脂温度、保圧値、保圧時間等）、温度依存性を考慮した樹脂と金型の物性データ（粘性、比容積、熱伝導率、比熱等）及び解析条件を定義し、流動解析用の入力データを作成する（ステップＳ２）。
【００８４】
ステップＳ２で作成された入力データに基づき、樹脂が金型内に充填する過程、及びその後の保圧冷却過程での金型を含めた流動解析を実施し（ステップＳ３）、圧力、温度等の解析結果を得る。
【００８５】
又、ステップＳ３における流動解析処理の実行時、この流動解析プログラムに構造解析用のデータ変換プログラムを組み込んでおくことにより（ステップＳ４）、ステップＳ１で付加された構造解析用の境界条件の設定に基づき、構造解析で使用される圧力、温度の初期データ、形状入力データを得る（ステップＳ５）。これにより、流動解析を終了した後、即座に構造解析が実行される。
【００８６】
ステップＳ３における流動解析から得られた温度、圧力の初期データ、荷重、拘束等の各種境界条件を含む形状入力データに基づき、樹脂の粘弾性的特性（クリープ、応力緩和）及び金型内での冷却時の成形品及び金型間の型拘束を考慮した構造解析を実施し（ステップＳ６）、変形量、応力、歪み等の解析結果を得る（ステップＳ７）。
【００８７】
この解析結果を評価し（ステップＳ８）、成形品の形状精度が要求される許容値内に収まっている場合、処理を終了する。一方、成形品の形状精度が要求される許容値内に収まっていない場合、ステップＳ１の処理に戻り、金型設計、成形条件パラメータを変更して繰り返し解析を行うことにより、成形品の形状精度の最適化を図ることが可能となる。
【００８８】
次に、樹脂の粘弾性的特性と成形品及び金型間の型拘束を考慮した構造解析の流れについて説明する。この解析の流れは実施の形態１における構造解析処理手順を示すフローチャート（図２）と全く同じである。
【００８９】
従って、ここでは図２６に示す熱収縮歪みの計算処理手順を示すフローチャートを用いて、熱構造連成解析の各ステップで求まる温度と応力の値から計算される静水圧とから、樹脂のＰＶＴ状態方程式により比容積を計算する手段、得られた比容積から線膨張係数を計算して次ステップでの熱歪増分を計算する具体的な手段について詳細に説明する。
【００９０】
図１のステップＳ３に示す流動解析の実施により、要素節点データ、境界条件、解析コントロールデータ等の構造解析入力データを読み込み（ステップＳ２０）、流動解析により温度、圧力の解析結果が既に作成されているので、これらのデータを初期値として入力し（ステップＳ２１）、構造解析（Ｓ６）を開始する。
【００９１】
先ず最初に、流動解析結果として読み込んだ圧力データＰ０
、温度データＴ０ を基に、ＰＶＴ状態方程式により比容積Ｖ０ を計算しておく（図２６のステップＳ３１，Ｓ３２）。図２６の処理では、初期値として要素番号ｎ、時間ｔを値０に設定しておく（ステップＳ３０）。尚、樹脂のＰＶＴ状態方程式には、一般に数式（３）で表わされるスペンサーギルモア式或は数式（４）で表されるＴａｉｔ式を用いる。
【００９２】
Ｖ（Ｔ，Ｐ）＝（Ｚ（Ｐ＋Ｗ）＋ＲＴ）／（Ｐ＋Ｗ） ・・・ （３）
ここで、Ｗ：定数、Ｒ：定数、Ｚ：定数である。
【００９３】
Ｖ（Ｔ，Ｐ）＝Ｚ（Ｔ）［１−Ｃ・ｌｎ（１＋Ｐ／Ｂ（Ｔ））・・・（４）
ここで、Ｂ（Ｔ）：圧力依存定数、Ｃ：定数、Ｚ（Ｔ）：定数
次に、解析時間刻みΔｔ毎に成形品の任意の場所における温度Ｔｎが求まると（ステップＳ３３，Ｓ３４）、ＰＶＴ状態方程式から時刻ｔ＝ｔ＋Δｔでの比容積Ｖｎを得る（ステップＳ３５）。図２７はＰＶＴ状態方程式から計算される比容積、温度、圧力の関係を示すグラフである。但し、この時点では、ＰＶＴ状態方程式での圧力Ｐは流動解析結果から初期値として読み込んだ圧力Ｐ０
である。
【００９４】
樹脂の等方性収縮を仮定した場合、時間刻みΔｔでの比容積（Ｖｎ−Ｖ０ ）と温度変化ΔＴから、数式（５）に従って線膨張係数αｎ を計算する（ステップＳ３６）。
【００９５】
αｎ ＝（（Ｖｎ ／Ｖ０ ）１／３ −１）／ΔＴ ・・・ （５）
このαｎ により、解析の第１ステップでの温度変化ΔＴに対する熱収縮歪ΔｅＶ が求まるので（ステップＳ３７）、これによりステップＳ２２，Ｓ２３での型拘束を考慮した粘弾性解析を実施して応力分布を求める（ステップＳ３８）。
【００９６】
尚、薄肉成形品等では、本出願人の過去の実験により、流れ方向（面内方向）と板厚方向とで異方性収縮挙動を示すことが確かめられている。この異方性収縮の取り扱い方法については、特開平７−１８６２２８号公報、特開平８−２３００８号公報において既に開示されており、数式（６）により異方性収縮歪ΔεＰを計算することができる。
【００９７】
ΔεＺ ＝Ａ＋Ｂ・ΔｅＶ
ΔεＰ ＝（ΔｅＶ −ΔεＺ）／２ ・・・ （６）
ここで、ΔεＺ ：板厚方向の収縮率、ΔεＰ ：面内方向の収縮率、Ａ，Ｂ：収縮係数、ΔｅＶ ：体積収縮率
ここで、ＰＶＴ状態方程式から求まる比容積を基に、線膨張係数或は熱収縮歪を求め、プラスチック成形品の形状精度を求める従来の構造解析手法は、充填保圧冷却過程での熱変形温度、固化温度或は流動停止温度等の収縮開始点における圧力温度分布と、常圧室温間での線膨張係数或は熱収縮歪を算出して線形弾性解析（熱応力解析）を行う方法である。従って、前記収縮開始点から室温に至る間の成形品の型拘束に伴なう応力緩和やクリープ等の負荷経路（時間）依存性については考慮していない。
【００９８】
本実施の形態では、金型と成形品全体が冷却されていく過程を非定常温度解析（ステップＳ２２）と負荷経路（時間）依存性を考慮できる粘弾性を考慮した構造解析（ステップＳ２３）を実施することで求めていく。この際、時間刻みΔｔ毎に成形品の任意の場所における温度Ｔｎ
、圧力（静水圧）Ｐｎ を求め、ステップＳ３５に示すＰＶＴ状態方程式から比容積Ｖｎ を算出して、熱収縮歪Δεを求める。
【００９９】
この粘弾性を考慮した構造解析（Ｓ２３）の具体的手法は、既に述べたように、時間−温度換算則が適用可能な熱レオロジー的に単純な材料と考え、時間−温度換算則にシフト関数、緩和弾性係数にプロニー級数を用いてマスターカーブ近似した線形粘弾性モデルを適用する。
【０１００】
尚、本発明では、樹脂の固化状態で得られる粘弾性マスターカーブではなく、前記実施の形態１で述べたように樹脂の固化状態と溶融状態でそれぞれで得られる動的粘弾性特性を１つに統合した粘弾性マスターカーブを作成し、緩和弾性係数、シフト関数にそれぞれ前述した数式（１），（２）を適用して用いる。
【０１０１】
次に、成形品表面と金型表面での型拘束の影響をより正確に取り扱う方法として、前述した実施の形態１では、ステップ毎の粘弾性を考慮した構造解析（Ｓ２３）を終了後、成形品表面及び金型表面において両者の接触距離（成形品と金型両方の接触面を構成する要素節点の距離）と接触面構成節点での反力により接触／解離判定を行う（ステップＳ２４）。接触判定時には成形品と金型の接触面に熱通過率を設定し、解離判定時には成形品表面とキャビティ空間の間に熱伝導率を設定して次回ステップの温度解析に反映していく解析方法について示した。しかし、この方法は、解析的に非線形性の非常に強い問題となる場合があり、解析モデル形状によっては安定した解析結果が得られない、或は計算コストが非常に掛かる等の問題があり、効率的ではない。
【０１０２】
そこで、本実施の形態では、通常の適正な成形品が得られる成形条件範囲では、成形品及び金型間の接触摩擦、すべり、解離等の要因が成形品の変形に与える影響は小さいと考え、保圧時の圧力による金型の変形と冷却固化に伴う成形品表面と金型表面での型拘束の影響を、成形品及び金型間の接触挙動がない一体型モデルとして考慮する。
【０１０３】
具体的には、成形品が取出し可能温度（離型温度）の金型から取り出されるまでは、成形品表面と金型表面において両者は完全に密着（固着）していると仮定し、接触問題としての解析を省略する。
【０１０４】
そして、成形品が取り出された（離型）後は、解析モデルの金型の部分を削除して成形品のみを対象にした粘弾性応力解析を実施し、離型直後の型拘束解放に伴うスプリングバック変形量及び成形品表面とキャビティ空間の間に熱伝導率を設定し、最終的に成形品の温度が室温になるまでの熱変形量を解析する。
【０１０５】
前述した非定常温度解析（Ｓ２２）、粘弾性を考慮した構造解析（Ｓ２３）の手順を成形条件として入力された成形品取り出し温度或は時間になるまで繰り返す（ステップＳ２５）。尚、ステップ２４の接触／解離判定は本実施形態では省略する。そして、取り出し条件になった時点で、離型処理（成形品が金型による拘束から解放）を行うが、前述したように、解析モデル上では金型と成形品は連続した一体モデルとして解析を行っているため、金型部分についてだけ無剛性として後の解析対象から除外することで、成形品の離型時のＳｐｒｉｎｇ Ｂｃｋ量を計算する（ステップＳ２６）。
【０１０６】
その後、これまで解析してきた成形品および金型間での熱伝導条件を、成形品から大気への熱伝達境界条件に変更し、引き続き、大気中での自然放冷に伴う自由収縮挙動を、成形品が室温になるまで、非定常温度解析（ステップＳ２６Ａ）及び粘弾性を考慮した構造解析（ステップＳ２６Ｂ）を繰り返すことで計算し（ステップＳ２６Ｃ）、最終的に変形量、応力、歪等の計算結果を出力する（ステップＳ２７）。
【０１０７】
［実施例２］
図２８は成形品形状を示す図である。
【０１０８】
図２８に示すように、上記解析手順を、外形の長さ１０２ｍｍ、幅１１．６ｍｍの矩形形状に半径Ｒ１＝２５９．２ｍｍ、半径Ｒ２＝１５６．１２ｍｍの光学面形状を有するトーリックレンズ形状を例として、光学面の母線方向（レンズ長手方向）の変形量（ベンディング量）を解析により求める場合を示す。解析全体の流れは、既に詳述した図１及び図２６の解析手順に従って進める。
【０１０９】
図２９はレンズ形状の金型も含めた金型全体モデルを示す図である。但し、レンズ幅の中心で長手方向に左右対称であるので、１／２のモデルとなっている。この金型全体モデルは、固定側、可動側それぞれの金型及び成形品から構成されるモデルである。
【０１１０】
そして、要素分割プリプロセッサによりモデル全体を、図３０に示すように、７０００程度の要素数に分割した後、対称面、金型及び成形品の材質領域、流入境界等の各種境界条件を定義し、流動解析用の入力データを作成する。図３０は要素分割された解析モデル全体を示す図である。図３１は要素分割された成形品部だけを示す図である。尚、流動解析後に実施する拘束条件等の構造解析用の境界条件も併せて付加する。解析で用いた成形条件は以下に示す通りである。
【０１１１】
・使用樹脂 ポリオレフィン系樹脂
・樹脂温度 ２７０℃
・充填時間 ３． ０ｓｅｃ
・金型温度 １２０℃（一定）
・保圧圧力 設定値 １０６０ｋｇｆ／ｃｍ２ （金型内実測値８４８ｋｇｆ／ｃｍ２ ）
・保圧時間 ３０ｓｅｃ
・冷却時間 １２０ｓｅｃ
最初に、樹脂が金型内に充填して保圧冷却される過程を流動解析により行うが、成形品及び金型間の熱移動を考慮するために、充填から保圧冷却過程全体に対して非定常熱伝導解析も同時に行う。解析プログラムは、市販されている汎用流体解析ソフトウェアを使用し、これに樹脂の非ニュートン流体としての性質である粘性が温度及びせん断速度に依存する関係式、即ち、数式（７）に示すように、べき指数則に基づく粘性方程式と、前述した数式（３）に示すように、保圧解析時に必要となる圧力、温度、比容積の関係式であるスペンサーギルモアのＰＶＴ状態方程式をソフトウェアに付属のユーザーサブルーチンを利用して定義する。
【０１１２】
μ＝Ａ・γＢ ・ｅｘｐ（Ｃ・Ｔ） … （７）
ここで、Ａ，Ｂ，Ｃは樹脂によって定まる定数である。
【０１１３】
Ｖ（Ｔ，Ｐ）＝（Ｚ０ （Ｐ＋Ｗ）＋ＲＴ）／（Ｐ＋Ｗ） ・・・ （３）
ここで、Ｗ：定数、Ｒ：定数、Ｚ０ ：定数である。
【０１１４】
又、これと同時に、このユーザーサブルーチンを使用して流動解析のすぐ後に実行する構造解析入力データを作成するデータ変換プログラムを組み込んでおくことにより、構造解析で使用するための圧力、温度データ、形状入力データが作成されるようにする。
【０１１５】
図３２は本解析で得られた充填解析時のメルトフロントの進行状況を示す図である。図３３は保圧開始後の圧力分布を示す図である。図３４は保圧冷却過程中における樹脂の流動が停止した時点（本解析例では、保圧開始後、２０ｓｅｃ後）の成形品の温度分布を示す図である。
【０１１６】
次に、保圧冷却過程が終了した後の成形品の冷却中の熱収縮挙動に関する解析は、流動解析時に使用した要素分割モデルをそのまま用い、流動解析時での樹脂の流動が停止した時点での温度・圧力の最終結果を初期データとして構造解析に取り込む。
【０１１７】
図３５は樹脂の流動が停止した時点での金型・成形品全体の温度分布を示す図である。図３６は成形品部の温度分布を示す図である。図３７は流動解析の圧力分布を構造解析での初期応力（圧縮応力）に変換した後の圧力分布を示す図である。
【０１１８】
引き続き離型時まで成形品及び金型間の非定常温度解析と、型拘束を考慮した構造解析を熱解析と連成しながら行っていく。尚、本解析では、金型及び成形品の部分を共に変形体として解析を行うが、成形品について粘弾性を考慮した熱応力解析を行う。
【０１１９】
この際、本来の解析では、金型と成形品の界面は、接触解析問題として考え、冷却固化に伴う成形品表面と金型表面での接触、解離等の型拘束の影響を考慮する。これは、例えば接触判定時には成形品と金型間熱通過率を設定し、解離判定時には成形品表面とキャビティ空間の間が断熱となるような熱伝達率の設定を行いながら解析を進めていくことが望ましい。しかし、通常の良品が得られる適正な成形条件下では、離型するまで金型と成形品の界面は固着（密着）しており、金型及び成形品間の解離は生じないと考えられるので、本解析では、この接触解析を除外して離型まで金型と成形品は一体であると見なして計算を簡略化する。これにより、解析時間は短縮され、解析業務の効率化を図るメリットがある。
【０１２０】
解析プログラムは、市販されている汎用非線形構造解析プログラムを使用し、樹脂である成形品部について、時間−温度換算則が適用可能な熱レオロジー的に単純な材料と考え、前述したプロニー級数による応力緩和関数の近似が可能な線形粘弾性構成式（数式（１））とシフト関数（数式（２））を、解析入力データ及びユーザーサブルーチンを用いて定義して解析を行う。
【０１２１】
一方、この過程では、同時に時間刻み毎における成形品の任意の場所における温度、圧力（静水圧）を求め、前述したＰＶＴ状態方程式（数式（３））から比容積を取得し、熱収縮歪を計算することで、圧力（静水圧）の影響を考慮した解析を行う。尚、本解析で使用した粘弾性物性値は、前述の実施の形態１で示したポリオレフィン系樹脂と同じものである。解析入力データは、既に流動解析の実行時に作成されているので、すぐに構造解析の実行が可能である。以上の計算を成形品取り出し時間である離型時（本解析では、冷却時間１２０ｓｅｃ）まで行う。
【０１２２】
離型時に達した時点で、離型処理（成形品が金型による拘束から解放）を行うが、前述したように、解析モデル上では金型と成形品は連続した一体モデルとして解析を行っているので、本実施の形態では金型部分についてのみ無剛性として解析対象から除外することで、成形品の離型時のＳｐｒｉｎｇ Ｂａｃｋ量を計算する。
【０１２３】
その後、これまで解析してきた成形品及び金型間での熱伝導条件を成形品から大気への熱伝導境界条件に変更し、引き続き大気中での自然放冷に伴う自由収縮挙動を成形品が室温になるまで非定常温度解析と粘弾性を考慮した構造解析を繰り返すことで、更に計算を進め、最終的な変形量、応力、歪等の計算結果を出力する。
【０１２４】
図３８はレンズ成形品の中央部の節点番号５７５，６３８，７０１において、解析開始時の金型による拘束下での冷却状態から離型時を経て、大気中での自然放冷で室温に至るまでの温度履歴を示す図である。
【０１２５】
図３９は金型から成形品を取り出し、室温に至った時点におけるレンズ成形品のＲ１光学面、Ｒ２光学面それぞれの母線方向の変形状態を、実測値と解析値で比較した図である。Ｒ１光学面では、レンズ成形品の変形量は実測値約１６μｍであるのに対して解析値は２５μｍであり、Ｒ２光学面では、実測値約４０μｍであるのに対して解析値１５μｍという結果である。
【０１２６】
又、図４０は他の複数のレンズ部品（Ａ，Ｂ，Ｃ，Ｄの４部品）について同じく母線方向ベンディング量について検証を行った結果を示した図である。図中に示すレンズ部品Ａ，Ｂは、レンズ長さがそれぞれ２６０ｍｍ、２４０ｍｍ程度の長尺トーリックレンズであり、レンズ部品Ｃ，Ｄは、レンズ長さがそれぞれ９０ｍｍ、５０ｍｍ程度のトーリックレンズである。図中の母線方向ベンディング量は、レンズ有効範囲内での実測値と解析値を比較して示している。
【０１２７】
更に、図４１はレンズ部品（Ｄ部品）について母線方向ベンディング（Ｒ１面）について、形状プロファイルの比較検証を行った結果を示した図であり、両者は良く一致している。最後に、図４２は、レンズ部品（Ｃ部品）でのゲート側、レンズ中央、反ゲート側のＲ１，Ｒ２面それぞれについて子線方向Ｒについて、形状検証を行った結果を示した図である。
【０１２８】
Ｒ１面、Ｒ２面ともに初期の設計値Ｒに対して、成形後は、半径ｒが小さくなる結果となり、その傾向は解析においても計算可能であることが分かる。又、図中のニュートン誤差は、設計値Ｒに対する成形後のｒについて、子線方向の光学有効幅ｄの範囲での最大偏差量をニュートン本数として換算した値であり、実測値と解析値は良く一致している。
【０１２９】
このように、レンズ成形品の変形量を本解析手法によりほぼ定量的に予測することが可能であり、過去の類似レンズ部品の実測値も参考にすれば、予め変形量を補正したイニシャルの金型を作成することが可能であり、金型製作費用とコストを大幅に削減可能である。
【０１３０】
以上、本実施の形態の射出成形プロセスのシミュレーション装置を示したが、各実施形態で示された解析処理を行う射出成形プロセスのシミュレーション装置は、例えば、周知のＣＰＵ、ＲＯＭ、ＲＡＭ、Ｉ／Ｏインターフェースを有するコンピュータ本体、キーボード、ＣＲＴディスプレイ、外部メモリ及びプリンタ等のコンピュータシステムから構成することが可能であり、ＣＰＵが外部メモリに記憶された各種プログラムモジュールを実行することにより、形状定義部１、流動解析部２及び構造解析部３の各機能が具体的に実現される。
【０１３１】
【発明の効果】
以上の説明で明らかなように、本発明によれば、樹脂の応力緩和やクリープ等の粘弾性的な性質を考慮して、最終的な成形品形状を精度良く予測することができる。又、樹脂の応力緩和やクリープ等の粘弾性的な性質及び成形品と金型の接触面での型拘束等の影響を考慮して、最終的な成形品形状を精度良く予測することができる。
【０１３２】
又、成形時の温度・圧力因子の影響を考慮し、樹脂の粘弾性的な性質や成形品と金型間の熱移動並びに接触面での型拘束等の影響を同時に考量して成形品の形状精度をより精度良く求めることができる。
【０１３３】
更に、コンピュータを使用して金型を製作する前に検討することができるので、最適な形状を決定するまでの検討時間を短縮することができ、金型製作、修正等のコストを低減することができる。
【図面の簡単な説明】
【図１】射出成形プロセスシミュレーション装置における全体の解析処理手順を示すフローチャートである。
【図２】ステップＳ６における樹脂の粘弾性的特性および金型内での冷却時の樹脂と金型と間の接触状態、離型状態等の型拘束を考慮した構造解析処理手順を示すフローチャートである。
【図３】矩形型試験片を用いる強制捩り法による動的粘弾性の測定装置の概略を示す図である。
【図４】円板試験片を用いるせん断法による動的粘弾性の測定装置の概略を示す図である。
【図５】固体領域から溶融遷移領域の各温度での捩り法による動的粘弾性測定により得られた貯蔵弾性率Ｇ’の角周波数依存性の測定結果を示すグラフである。
【図６】固体領域から溶融遷移領域の各温度での捩り法による動的粘弾性測定により得られた損失弾性率Ｇ”の角周波数依存性の測定結果を示すグラフである。
【図７】溶融遷移領域から溶融領域の各温度でのせん断法による動的粘弾性測定により得られた貯蔵弾性率Ｇ’の角周波数依存性の測定結果を示すグラフである。
【図８】溶融遷移領域から溶融領域の各温度でのせん断法による動的粘弾性測定により得られた損失弾性率Ｇ”の角周波数依存性の測定結果を示すグラフである。
【図９】図５の捩り法による動的粘弾性測定により得られた各温度での貯蔵弾性率Ｇ’をシフトして重ね合わせた後の貯蔵弾性率の周波数依存性を示すグラフである。
【図１０】図６の捩り法による動的粘弾性測定により得られた各温度での損失弾性率Ｇ”をシフトして重ね合わせた後の損失弾性率の周波数依存性を示すグラフである。
【図１１】図７のせん断法による動的粘弾性測定により得られた各温度での貯蔵弾性率Ｇ’を重ね合わせた後の貯蔵弾性率の周波数依存性を示すグラフである。
【図１２】図８のせん断法による動的粘弾性測定により得られた各温度での損失弾性率Ｇ”を重ね合わせた後の損失弾性率の周波数依存性を示すグラフである。
【図１３】図９及び図１０で重ね合わせ時にシフトした移動因子（シフトファクタ）の温度依存性を示すグラフである。
【図１４】図１１及び図１２で重ね合わせ時にシフトした移動因子（シフトファクタ）の温度依存性を示すグラフである。
【図１５】せん断法での結果を捩じり法での基準温度１３８℃上に重ね合わせた貯蔵弾性率Ｇ’、損失弾性率Ｇ”の時間依存性に関するマスターカーブを示すグラフである。
【図１６】図１３及び図１４を更に重ね合わせ時の移動因子（ｌｏｇａＴ）の温度依存性を示すグラフである。
【図１７】図１５から得られた貯蔵弾性率Ｇ’、損失弾性率Ｇ”を変換して数式（１）に示すプロニー級数近似し、温度に対する緩和弾性係数Ｇ（ｔ）の関係を示すグラフである。
【図１８】図１６から得られた時間−温度移動因子を数式（２）に示す多項式により近似し、両者を比較したグラフである。
【図１９】具体的な成形品形状を示す図である。
【図２０】図１９の厚肉平板も含めた金型全体モデルの形状を示す図である。
【図２１】５０００要素に分割された金型全体モデルを示す図である。
【図２２】流動解析で得られた保圧冷却過程が終了した時点（樹脂の流動が停止した時点）の成形品の温度分布を示す図である。
【図２３】金型全体モデルの温度分布を示す図である。
【図２４】冷却に伴う樹脂の体積収縮によりキャビティ内で成形品が金型から解離している成形品表面部分（樹脂流入口側）で断熱作用により温度が高く、金型に接している成形品表面部分で温度低下を生じている例を示す図である。
【図２５】本解析で得られた金型から成形品を取り出した時点の成形品の変形を示す図である。
【図２６】熱収縮歪みの計算処理手順を示すフローチャートである。
【図２７】ＰＶＴ状態方程式から計算される比容積、温度、圧力の関係を示すグラフである。
【図２８】成形品形状を示す図である。
【図２９】レンズ形状の金型も含めた金型全体モデルを示す図である。
【図３０】要素分割された解析モデル全体を示す図である。
【図３１】要素分割された成形品部だけを示す図である。
【図３２】本解析で得られた充填解析時のメルトフロントの進行状況を示す図である。
【図３３】保圧開始後の圧力分布を示す図である。
【図３４】保圧冷却過程中における樹脂の流動が停止した時点（本解析例では、保圧開始後、２０ｓｅｃ後）の成形品の温度分布を示す図である。
【図３５】樹脂の流動が停止した時点での金型・成形品全体の温度分布を示す図である。
【図３６】成形品部の温度分布を示す図である。
【図３７】流動解析の圧力分布を構造解析での初期応力（圧縮応力）に変換した後の圧力分布を示す図である。
【図３８】レンズ成形品の中央部の節点番号５７５，６３８，７０１において、解析開始時の金型による拘束下での冷却状態から離型時を経て大気中での自然放冷で室温に至るまでの温度履歴を示す図である。
【図３９】金型から成形品を取り出し、室温に至った時点におけるレンズ成形品のＲ１光学面、Ｒ２光学面それぞれの母線方向の変形状態を実測値と解析値で比較した図である。
【図４０】各種レンズ部品（Ａ，Ｂ，Ｃ，Ｄの４部品）での母線方向ベンディング量について検証を行った結果を示した図である。
【図４１】レンズ部品（Ｄ部品）での母線方向ベンディング（Ｒ１面）について形状プロファイルの検証を行った結果を示した図である。
【図４２】レンズ部品（Ｃ部品）でのゲート側、レンズ中央、反ゲート側のＲ１，Ｒ２面それぞれについて子線方向Ｒについて形状検証を行った結果を示した図である。
【符号の説明】
１ 形状定義部
２ 流動解析部
３ 構造解析部
１１ 金型全体モデル
１１ａ 固定側金型
１１ｂ 可動側金型
１１ｃ 成形品[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an injection molding process simulation apparatus and a shape accuracy prediction method for supporting optimal setting of a mold design, molding conditions, and the like in order to increase the shape accuracy of a molded product in an injection molding method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in order to increase the shape accuracy of a molded product in plastic injection molding, various analysis systems that support optimal design of a mold, molding conditions, and the like have been used.
[0003]
For example, a heat transfer analysis system for predicting the optimal cooling of the molten resin in the mold, a flow analysis system for predicting the pressure, temperature distribution, etc. in the filling and holding pressure cooling process of the molten resin, molds and molded products There is known a structural analysis system or the like for estimating the strength of steel and the amount of deformation accompanying molding shrinkage.
[0004]
These analysis systems are used individually or in combination according to each situation by a numerical analysis method such as a finite element method, a boundary element method, or the like on a modeled mold and resin flow path shape. As a prior art relating to these analysis systems, for example, a “forming process simulation” described in Japanese Patent Publication No. Hei 6-22840, an “integrated die analysis system” described in Japanese Patent No. 2540232, and the like are known.
[0005]
Japanese Patent Publication No. Hei 6-22840 discloses a "molding process simulation" that specifies a point in time at which the connection of a molten phase of a resin in a mold is cut off for a plastic lens molded product, and determines the temperature of the resin at this point. A method of obtaining a shape accuracy by performing a thermal stress analysis using a temperature change in a cooling process until a molded product uniformly reaches room temperature as an initial temperature as a thermal load is described.
[0006]
Japanese Patent No. 2,540,232 discloses a method for optimizing a flow path in a mold by performing a combination of heat transfer analysis, flow analysis, and structural analysis. .
[0007]
Further, in Japanese Patent Application Laid-Open No. Hei 5-169506, "Molding Process Simulation Method and Apparatus" and in Japanese Patent Application Laid-Open No. 6-55597, "Injection Molding Process Simulation Method and Apparatus" By sequentially performing the cooling analysis means and calculating the pressure, temperature change, and specific volume change of the molding resin during the injection molding process, the specific volume at the atmospheric pressure of the resin pressure or at the time of mold release and the specific volume at the room temperature are obtained. A method of calculating a shrinkage strain from a difference and performing a structural analysis to predict a shape accuracy of a molded product such as warpage or sink mark is disclosed. These conventional analysis methods are summarized as follows.
[0008]
1) As a heat transfer analysis means considering both the mold and the molded product at the same time, a steady-state temperature analysis using a molding cycle, a heat supply amount of a resin, a heat discharge amount from a water pipe and a mold surface, and a steady-state temperature analysis obtained from the above-mentioned steady-state temperature analysis. Using the obtained mold cavity surface temperature as needed, we perform filling pressure-holding cooling analysis.
[0009]
2) Shrinkage strain required during structural analysis is due to the point at which the molten resin is cooled to the thermal deformation temperature, solidification temperature, and flow stop temperature during the filling pressure-holding cooling process, or the supply of resin that compensates for volume shrinkage is interrupted. A method in which the time point is defined as a shrinkage starting point, and a temperature difference of the molded article at the shrinkage start point, a temperature difference at room temperature (the molded article uniformly reaches room temperature), and a coefficient of linear expansion of the molded article are determined. Also, a method of determining from the difference between the specific volume obtained from the temperature distribution and the pressure distribution at the shrinkage starting point using the PVT equation of state and the specific volume at room temperature, The method is determined from the stress generated (residual stress) and the specific volume difference (linear expansion coefficient) from the temperature and pressure during demolding to room temperature.
[0010]
3) Structural analysis for obtaining final shape accuracy is obtained by performing linear elasticity analysis (thermal stress analysis) using contraction strain from the difference in specific volume.
[0011]
[Problems to be solved by the invention]
However, in order to predict the more accurate shape accuracy of plastic molded products by analysis, filling and holding pressure cooling analysis using the mold cavity surface temperature obtained from the steady-state temperature analysis described above, A method of performing linear elasticity analysis (thermal stress analysis) based on shrinkage strain is insufficient. For example, it is known that the shape accuracy of a plastic molded product changes greatly depending on the time from the start of molding to the time of removing the molded product and the cooling gradient during that time.In general plastic parts, the cooling time is longer than when the cooling time is short. It is known that the case has better warpage deformation accuracy.
[0012]
This is because, as is well known, resin is a material having viscoelastic properties represented by creep and stress relaxation, and is held longer at a higher temperature in a mold. This is because the internal stress in the molded product is reduced.
[0013]
Further, when the resin is cooled and solidified in the mold, the molded product is restrained by the mold, hindering free shrinkage, and there are many portions where internal stress is accumulated.
[0014]
In such a constrained portion of the mold, the stress level and the degree of time change are different from those of other unconstrained portions, and when the molded product is taken out, for example, a stress such as springback is released. Deformation occurs.
[0015]
In order to more accurately obtain the shape accuracy of a molded product having such factors, a certain point in the above-described molten resin filling and holding pressure cooling process is set as a shrinkage start point, and thereafter, the resin reaches room temperature. Temperature change up to the thermal load based on the coefficient of linear expansion and performing a linear elasticity analysis (thermal stress analysis), or a linear elasticity analysis using the pressure and temperature change until the resin reaches room temperature as a heat shrinkage strain ( The method obtained by performing thermal stress analysis) is insufficient because it cannot explain phenomena such as the shape accuracy changing depending on the cooling time.
[0016]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide an injection molding process simulation apparatus and a shape accuracy prediction apparatus capable of performing optimal setting support of a mold design, molding conditions, and the like of a plastic molded product. It is to provide a method.
[0017]
[Means for Solving the Problems]
In the present invention, the following three factors are considered for the above-described problem.
[0018]
1) In the entire process from the filling / holding / cooling process to the release of the molded product to the room temperature, the filling / holding / cooling analysis is performed in consideration of the unsteady heat transfer between the mold and the molded product.
[0019]
2) Perform structural analysis taking into account viscoelasticity represented by creep and stress relaxation of the resin.
[0020]
At this time, viscoelastic properties (master curve) obtained by integrating the viscoelastic properties obtained in the solidified state of the resin or the dynamic viscoelastic properties obtained from the solidified state and the molten state of the resin into one are created. use.
[0021]
3) In the case where there is a contact behavior between the molded product and the surface of the mold in the mold, and in the case where there is no contact behavior, a structural analysis is performed in consideration of the influence of any mold constraint.
[0022]
That is, the pressure distribution and temperature distribution of the molded product at the shrinkage start point determined during the filling pressure-holding cooling analysis are set as initial values in the structural analysis based on viscoelasticity represented by resin creep and stress relaxation. The cooling proceeds while being restrained, the mold is released from the mold, and shrinkage determined by the PVT equation of state from the pressure (hydrostatic pressure) and the temperature of each part of the molded product in each time step of reaching room temperature by releasing heat to the atmosphere. Structural analysis based on viscoelastic theory is carried out by using strain sequentially.
[0023]
As a result, for a molded product such as a plastic optical element that requires high-precision shape accuracy, an analysis model that considers the mold and molded product simultaneously in the entire process from flow holding pressure cooling analysis to structural analysis Use, especially considering the effects of temperature and pressure factors during molding, and the effects of viscoelastic properties such as stress relaxation and creep of the resin, unsteady heat transfer between molded products and molds, and mold constraints. Is taken into account at the same time, and the shape accuracy of the molded article can be obtained more accurately.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of an injection molding process simulation apparatus and a shape accuracy prediction method according to the present invention will be described.
[0025]
In the first embodiment, the outline of the injection molding process simulation apparatus and the shape accuracy prediction method are generally described, and the viscoelastic properties obtained in the solidified state of the resin, or the dynamic viscosities obtained from the solidified state and the molten state of the resin, respectively. A method for creating and using a viscoelastic characteristic (master curve) in which elastic characteristics are integrated into one will be described in detail. Further, in the second embodiment, a more specific method for applying to an actual lens molded product will be described in detail including an example.
[0026]
<Embodiment 1>
FIG. 1 is a flowchart showing the overall analysis processing procedure in the injection molding process simulation apparatus.
[0027]
The injection molding process simulation apparatus basically includes a shape definition unit 1 that performs element division and creates an analysis model by performing element division used in analysis such as a finite element method, and includes a heat transfer analysis of a mold and a resin. Flow analysis unit 2 that analyzes the filling, holding and cooling process, and structural analysis that considers the viscoelastic properties such as resin creep and stress relaxation and the mold constraint between the mold and the molded product during resin cooling It has a structural analysis unit 3 for performing the whole analysis processing by the function of each of these units.
[0028]
First, shape definition and mesh division are performed (step S1). In the process of step S1, a CAD system or the like defines the shape of a mold and a molded product to be analyzed, and then performs element division such as a finite element method by an element division preprocessor to create an analysis model. It is to be noted that the shape is fetched by using the CAD interface as needed.
[0029]
In the analysis according to the present embodiment, a structural analysis is performed subsequent to the flow analysis. Therefore, when performing shape definition and mesh division, boundary conditions for structural analysis such as constraint conditions are added in advance.
[0030]
After that, the physical property data (viscosity, specific volume, thermal conductivity, specific heat, etc.), molding conditions (injection speed, resin temperature, holding pressure value, holding time, etc.) and analysis conditions of the resin and mold for analysis are Define and create input data for flow analysis (step S2).
[0031]
Based on the input data created in step S2, a flow analysis including the mold in the process of filling the mold with the resin and the subsequent holding pressure cooling process is performed (step S3), and the pressure, temperature, etc. Obtain analysis results.
[0032]
At the time of executing the flow analysis processing in step S3, by incorporating a data conversion program for structural analysis into this flow analysis program (step S4), the boundary conditions for structural analysis added in step S1 can be set. Based on this, initial pressure and temperature data and shape input data used in the structural analysis are obtained (step S5). Thus, the structural analysis is performed immediately after the flow analysis is completed.
[0033]
Based on initial data of temperature and pressure, shape input data including various boundary conditions such as loads and constraints obtained from the flow analysis in step S3, the viscoelastic properties (creep, stress relaxation) of the resin and the A structural analysis is performed in consideration of the mold constraint (contact state) between the resin and the mold during cooling (step S6), and analysis results such as deformation, stress, and distortion are obtained (step S7).
[0034]
The result of this analysis is evaluated (step S8), and if the shape accuracy of the molded product falls within the required tolerance, the process ends. On the other hand, if the shape accuracy of the molded product is not within the required tolerance, the process returns to step S1, and the mold design and the molding condition parameters are changed and the analysis is repeated to obtain the shape accuracy of the molded product. Can be optimized.
[0035]
FIG. 2 is a flowchart showing a structural analysis processing procedure in consideration of the viscoelastic characteristics of the resin in step S6 and a mold constraint such as a contact state between the resin and the mold at the time of cooling in the mold and a mold release state. .
[0036]
Since the element nodal data, boundary conditions (temperature, load, constraint data), structural control input data such as analysis control data, and temperature and pressure analysis results have already been created by the flow analysis in step S3, these data are used. The structure analysis is performed by using (Steps S20 and S21).
[0037]
First, based on the temperature data read as a result of the flow analysis, the subsequent cooling of the mold and the entire molded product is determined by performing an unsteady temperature analysis (step S22). In this process, the temperature change at an arbitrary position of the molded article at each time interval is obtained, and therefore, the thermal contraction strain is obtained from the linear expansion coefficient of the resin or the PVT equation of state, and the viscoelasticity is considered in consideration of this value. A structural analysis is performed (step S23).
[0038]
In this structural analysis, the mold portion is considered as a deformable body (elastic body) or a rigid body depending on the application. The former is a case where deformation due to thermal distortion of the mold cannot be ignored, and the latter is a case where it can be ignored. A linear viscoelastic model that considers the resin molded part as a thermorheologically simple material, that is, as a model to which the time-temperature conversion rule can be applied, and that can approximate the relaxed elastic modulus by a shift function and a Prony series. And analyze it. Equations (1) and (2) are used as a stress relaxation function (Prony series) and a shift function, respectively. Note that the time-temperature conversion rule is a temperature T0 as a certain reference.
, The behavior at higher temperatures corresponds to short-time behavior at the reference temperature, and the behavior at low temperatures corresponds to long-time behavior at the reference. That is, time and temperature can be equivalently converted.
[0039]
(Equation 1)

Here, G∞: equilibrium elastic modulus, t ′: relaxation time, λn
: Coefficient of relaxation time.
[0040]
log10AT (T) = C0 + C1.T + C2.T2 + C3.T3 + C4.T4 + ... + Cn.Tn ... (2)
Here, log10AT (T): temperature shift factor, Cn: coefficient, and T: temperature.
[0041]
Here, when performing the structural analysis in consideration of the viscoelasticity in step S23, the temperature behavior of the resin as the molded product is such that the vicinity of the mold wall surface is in a solidified state during flow, but the inside of the molded product is in a molten state. Then, the two phases are gradually cooled and solidified in a mixed state. Therefore, the viscoelastic master curve of the resin needs not only a solid state but also a molten state. Therefore, if one viscoelastic master curve can be created and used over the entire region from the solidified state to the molten state, the viscoelastic properties in the molten state are accurately taken into consideration, which is very efficient and effective.
[0042]
Therefore, a method of obtaining a viscoelastic property value used in the structural analysis in consideration of the viscoelasticity in step S23 will be described in detail by taking a case of a polyolefin resin as an example.
[0043]
The viscoelasticity test methods include a forced torsion method (angular frequency sweep) using a rectangular test piece (thickness 2.5 mm, width 12 mm, length 40 mm) in the solid region of the resin, and cone / disc treatment when the resin is melted. A shearing method (angular frequency sweep) using a disk test piece (2.5 mm in thickness, 25 mm in diameter) inserted between the tools was applied.
[0044]
FIG. 3 is a view schematically showing an apparatus for measuring dynamic viscoelasticity by a forced torsion method using a rectangular test piece.
[0045]
In this method, the lower end of the test piece is connected to the vibration motor, and the upper end is connected to the transducer for torque detection. After fixing both ends of the rectangular test piece with the chuck, the angular frequency is fixed to the other end with one end fixed. Apply sinusoidal torsional displacement. This is a viscoelasticity measurement method for measuring the torque generated at this time.
[0046]
The torsional strain amplitude generated in the test specimen is determined from the thickness, width, and distance between the chucks of the rectangular test specimen, and the storage elastic modulus G 'and viscosity related to the energy stored elastically when the test specimen is deformed The loss elastic modulus G ″ related to the energy that has been physically lost can be obtained.
[0047]
FIG. 4 is a diagram schematically showing an apparatus for measuring dynamic viscoelasticity by a shear method using a disk test piece.
[0048]
This method is based on the torque generated when a specimen is inserted between a cone and a disc-shaped metal jig connected to a motor and a transducer, respectively, and a sinusoidal deformation of angular frequency and rotation amplitude is applied to the sample from the cone. Is a method of measuring
[0049]
The strain amplitude is determined from the radius of the disk, the angle between the cone and the disk, and the storage elastic modulus G 'related to the energy stored elastically when the test piece is deformed and the energy lost viscously The associated loss modulus G "can be determined.
[0050]
As a measuring device, a rheometric viscoelastic spectrometer is used. In a temperature range of 23 ° C. to 190 ° C., which is a transition region from a solid region, a forced torsion method is used. The measurement was performed by a shearing method in a temperature range of up to 300 ° C. The angular frequency was given in the range of 0.1 to 100 rad / s, and the distortion amplitude was given in the range of 0.1 to 10%.
[0051]
FIG. 5 is a graph showing the measurement results of the angular frequency dependence of the storage elastic modulus G ′ obtained by the dynamic viscoelasticity measurement by the torsion method at each temperature from the solid region to the melting transition region, and FIG. FIG. 7 is a graph showing the measurement results of the angular frequency dependence of the loss elastic modulus G ″ obtained by the dynamic viscoelasticity measurement by the torsion method at each temperature in the transition region. FIG. FIG. 8 is a graph showing the measurement results of the angular frequency dependence of the storage elastic modulus G ′ obtained by the dynamic viscoelasticity measurement by the shearing method. FIG. 8 shows the dynamic viscoelasticity by the shearing method at each temperature from the melting transition region to the melting region. It is a graph which shows the measurement result of the angular frequency dependence of the loss elastic modulus G "obtained by the measurement.
[0052]
From these measurement results, by applying the temperature-time conversion rule, the reference temperature (138 ° C. in the case of the present resin in the torsion method from the solid region to the melt transition region, and the shear temperature in the melt transition region to the melt region). Method, the storage elastic modulus G ′ and the loss elastic modulus G ″ at each measurement temperature obtained by the torsion method and the shear method are sequentially moved on the time axis (horizontal movement) and overlapped. These results are shown in FIGS. 9 and 10 for the twisting method and in FIGS. 11 and 12 for the shearing method.
[0053]
FIG. 9 is a graph showing the frequency dependence of the storage modulus after shifting and superposing the storage modulus G 'at each temperature obtained by the dynamic viscoelasticity measurement by the torsional method of FIG. FIG. 10 is a graph showing the frequency dependence of the loss modulus after shifting and superimposing the loss modulus G ″ at each temperature obtained by the dynamic viscoelasticity measurement by the torsion method of FIG. Fig. 11 is a graph showing the frequency dependence of the storage elastic modulus after superimposing the storage elastic modulus G 'at each temperature obtained by the dynamic viscoelasticity measurement by the shear method in Fig. 7. Fig. 12 is Fig. 8. 7 is a graph showing the frequency dependence of the loss elastic modulus after superimposing the loss elastic modulus G ″ at each temperature obtained by the dynamic viscoelasticity measurement by the shear method of FIG.
[0054]
As shown in the above figures, it can be seen that the storage modulus G ′ and the loss modulus G ″ at each measurement temperature can all be superimposed on the reference temperature. It indicates that the material is a thermorheologically simple material that satisfies the time conversion rule, and the curve of the storage modulus G ′ and the loss modulus G ″ which are all superimposed on this reference temperature is called a master curve. FIG. 13 is a graph showing the movement amount of each curve at the time of superposition in the torsion method as a movement factor (shift factor). FIG. 14 is a graph showing the movement amount of each curve at the time of superposition in the shearing method as a movement factor (shift factor).
[0055]
Next, the master curves of the storage elastic modulus G ′ and the loss elastic modulus G ″ obtained by both the twisting method and the shearing method are further superimposed, and one curve is formed from the solid region of the resin to the entire region of the molten region. FIG. 15 shows the results of the storage modulus G ′ and the loss modulus G ″ obtained by superimposing the results obtained by the shearing method on a reference temperature of 138 ° C. by the torsion method. It is a graph which shows the master curve regarding time dependency. FIG. 16 shows a transfer factor (logaT) when FIGS. 13 and 14 are further superimposed.
3 is a graph showing the temperature dependence of FIG.
[0056]
From this result, it can be seen that one viscoelastic master curve can be created from the solid region of the resin to the entire molten region.
[0057]
In order to finally use the master curve of the storage elastic modulus G ′ and the loss elastic modulus G ″ in the linear viscoelastic analysis, the relaxation spectrum is calculated from the storage elastic modulus G ′ and the loss elastic modulus G ″. Then, it is necessary to obtain the relaxation elastic modulus and to approximate the Prony series from this.
[0058]
FIG. 17 is a graph showing the relationship between the relaxation elastic coefficient G (t) and the temperature by converting the storage elastic modulus G ′ and the loss elastic modulus G ″ obtained from FIG. 18 is a graph in which the time-temperature transfer factor obtained from FIG. 16 is approximated by a polynomial expression shown in Expression (2), and the two are compared.
[0059]
As described above, the viscoelastic properties of the resin as the molded article are measured in a solidified state (forced torsion method) and a molten state (shear method) by a dynamic viscoelasticity test method, and the two are superimposed to form a Prony series ( One master curve using a relaxation elastic modulus) and a shift function (time-temperature conversion rule) can be created, and it can be analyzed by applying a linear viscoelastic model.
[0060]
In the present invention, not only the viscoelastic master curve obtained in the solidified state of the resin, but also create a viscoelastic master curve integrating the dynamic viscoelastic properties obtained in each of the solidified state and the molten state of the resin into one, It is characterized in that a structural analysis for obtaining a deformation behavior of the shape of a mold or a plastic molded article due to thermal shrinkage is performed using the physical property values.
[0061]
Further, at the same time as carrying out the structural analysis in consideration of the above viscoelastic properties, the effects of mold constraints such as contact and dissociation between the surface of the molded product and the surface of the mold due to cooling and solidification are also considered. Specifically, after the stress analysis for each step (Step S23) is completed, the contact distance between the molded product surface and the mold surface (distance between element nodes constituting the contact surface between the molded product and the mold) Then, the contact / dissociation determination is made based on the reaction force at the node constituting the contact surface (step S24).
[0062]
At the time of contact determination, the heat transfer coefficient at the contact surface between the molded product and the mold is set, and at the time of dissociation determination, the heat transfer coefficient between the molded product surface and the cavity space is set and reflected in the temperature analysis in the next step.
[0063]
The procedure of the unsteady temperature analysis (step S22), the structural analysis taking viscoelasticity into consideration (step S23), and the determination of contact / dissociation (step S24) are used as the molding condition taking-out temperature or taking-out time inputted as the molding condition. (Step S25), and when this condition (temperature or time) is reached, calculation of the spring back (Spring Back) amount of the molded product due to the release processing (the molded product is released from the constraint by the mold) is performed. (Step S26), and thereafter, a structural analysis is performed in consideration of viscoelasticity until it is naturally cooled in the air and reaches room temperature, and finally calculation results such as deformation, stress, and strain are output (Step S26). S27). Thereafter, the analysis processing ends.
[0064]
[Example 1]
Next, a specific example of the analysis processing will be described.
[0065]
FIG. 19 is a diagram showing a specific molded product shape. This molded product is a simple thick flat plate of 60 mm × 60 mm (6 mm in thickness) having a gate shape of 20 mm × 20 mm (6 mm in thickness). The entire analysis process is performed according to the procedure of FIG.
[0066]
FIG. 20 is a diagram showing the shape of the entire mold including the thick flat plate of FIG. Since the entire mold model 11 is bilaterally symmetric, FIG. 20 shows only a half of the model part. The entire mold model 11 is a model including a fixed mold 11a, a movable mold 11b, and a molded product 11c.
[0067]
FIG. 21 is a diagram showing a whole mold model divided into 5000 elements. As shown in FIG. 21, the whole mold model is divided into about 5000 elements by the element division preprocessor, and various boundary conditions such as a symmetry plane, a material area of the mold and the molded product, an inflow boundary, and the like are defined. Create input data for analysis. It should be noted that boundary conditions for structural analysis such as constraint conditions to be performed after the flow analysis are also added.
[0068]
First, the flow analysis analyzes the process in which the resin is filled in the mold and is cooled under pressure. As this analysis program, commercially available general-purpose fluid analysis software is used, and the viscosity, which is the property of resin as a non-Newtonian fluid, depends on temperature and shear rate, that is, the viscosity equation and the packing pressure analysis The required pressure, temperature, and PVT state equation, which is a relational expression of the specific volume, are defined using a user subroutine attached to the software.
[0069]
At the same time, by incorporating a data conversion program for creating input data for structural analysis to be executed immediately after flow analysis using this user subroutine, pressure and temperature data for use in structural analysis, The shape input data is created.
[0070]
FIG. 22 is a diagram showing the temperature distribution of the molded product at the time when the pressure-holding cooling process obtained by the flow analysis is completed (when the flow of the resin is stopped). In the figure, the temperature distribution is represented by shading, where the temperature at the point a on the gate side is the highest, the temperature at the point b is also high, and the temperature at the point c in contact with the mold is the lowest. The temperature range in this case is 183 ° C to 93 ° C.
[0071]
Next, the heat shrinkage behavior during cooling of the molded product after the pressure holding process is completed is incorporated into the structural analysis using the final results of temperature and pressure in flow analysis as initial data, and viscoelastic analysis taking into account mold constraints is performed. Do.
[0072]
FIG. 23 is a diagram showing a temperature distribution of the whole mold model.
[0073]
In the drawing, the temperature distribution is represented by shading, where the temperature at point d on the gate side is the highest, the temperature at point e is also high, and the temperature at point f in the mold portion is the lowest. In this analysis, as shown in FIG. 23, the temperature analysis is performed on the entire mold and the molded product, but the viscoelasticity analysis is performed on the mold part as a rigid body. Since the analysis input data has already been created at the time of executing the flow analysis, it can be immediately executed.
[0074]
A commercially available general-purpose nonlinear structural analysis program is used as an analysis program, and the molded product portion, which is a resin, is considered to be a thermorheologically simple material to which the time-temperature conversion rule can be applied. The analysis is performed by using a linear viscoelastic model capable of defining the relaxation elastic modulus according to (1)) and defining the shift function (formula (2)) using a user subroutine.
[0075]
Also, the effects of mold constraints such as contact and dissociation between the surface of the molded product and the surface of the mold due to cooling and solidification are considered. The heat transfer rate is set so that the temperature of the contact surface between the molded product and the mold is the same at the time of contact determination, and the heat transfer coefficient is set at the time of dissociation determination so that the space between the molded product surface and the cavity space is insulated. I do.
[0076]
FIG. 24 shows a molded product in which the temperature is high due to heat insulation at the surface of the molded product (resin inlet side) where the molded product is dissociated from the mold in the cavity due to the volume shrinkage of the resin due to cooling, and the molded product is in contact with the mold. FIG. 4 is a diagram illustrating an example in which a temperature drop occurs at a surface portion. In the figure, the temperature distribution is represented by shading, where the temperature at point g on the gate side (resin inlet side) is the highest, and the temperature at point h on the surface portion in contact with the mold is low.
[0077]
At the time when the removal time finally set as the molding condition is reached, in order to analyze the springback behavior of the molded product at the time of release, a process for removing the influence of the mold constraint of the molded product by the mold is performed, and then, The analysis is performed up to room temperature after being naturally cooled in the atmosphere to obtain the final results of the deformation amount, stress, and the like.
[0078]
FIG. 25 is a view showing the deformation of the molded product at the time when the molded product is taken out from the mold obtained by the present analysis. In addition, in order to make the deformation state in the figure easy to understand, the result is shown in a state where the display magnification is increased.
[0079]
<Embodiment 2>
Next, an injection molding process simulation apparatus according to Embodiment 1 of the present invention will be described. The same components as those in the first embodiment are denoted by the same reference numerals.
[0080]
The injection molding process simulation apparatus according to the present embodiment creates an analysis model by basically defining a shape and performing element division used in analysis such as the finite element method, similarly to FIG. 1 of the first embodiment. A shape definition unit 1, a flow analysis unit 2 that includes an analysis of a filling pressure-holding cooling process including a heat transfer analysis between a mold and a resin, and a viscoelastic property such as creep and stress relaxation of the resin and a resin cooling time. The apparatus has a structural analysis unit 3 that performs a structural analysis in consideration of a mold constraint between a mold and a molded product, and performs the entire analysis processing by the functions of these units.
[0081]
First, shape definition and mesh division are performed (step S1). In the process of step S1, a CAD system or the like defines the shape of a mold and a molded product to be analyzed, and then performs element division by an element division preprocessor using a finite element method or the like to create an analysis model. It is to be noted that the shape is fetched by using the CAD interface as needed.
[0082]
In the analysis according to the present embodiment, a structural analysis is performed subsequent to the flow analysis. Therefore, when performing shape definition and mesh division, boundary conditions for structural analysis such as constraint conditions are added in advance.
[0083]
After that, the molding conditions (injection speed, resin temperature, dwelling time, dwelling time, etc.) for the analysis, and the physical properties data of the resin and mold in consideration of temperature dependency (viscosity, specific volume, thermal conductivity, specific heat) Etc.) and analysis conditions are defined, and input data for flow analysis is created (step S2).
[0084]
Based on the input data created in step S2, a flow analysis including the mold in the process of filling the mold with the resin and the subsequent holding pressure cooling process is performed (step S3), and the pressure, temperature, etc. Obtain analysis results.
[0085]
At the time of executing the flow analysis processing in step S3, by incorporating a data conversion program for structural analysis into this flow analysis program (step S4), the boundary conditions for structural analysis added in step S1 can be set. Based on this, initial pressure and temperature data and shape input data used in the structural analysis are obtained (step S5). Thus, the structural analysis is immediately performed after the flow analysis is completed.
[0086]
Based on initial data of temperature and pressure, shape input data including various boundary conditions such as loads and constraints obtained from the flow analysis in step S3, the viscoelastic properties (creep, stress relaxation) of the resin and the A structural analysis is performed in consideration of the mold constraint between the molded product and the mold at the time of cooling (step S6), and analysis results such as deformation, stress, and distortion are obtained (step S7).
[0087]
The result of this analysis is evaluated (step S8), and if the shape accuracy of the molded product falls within the required tolerance, the process ends. On the other hand, if the shape accuracy of the molded product is not within the required tolerance, the process returns to step S1, and the mold design and the molding condition parameters are changed and the analysis is repeated to obtain the shape accuracy of the molded product. Can be optimized.
[0088]
Next, the flow of the structural analysis in consideration of the viscoelastic properties of the resin and the mold constraint between the molded product and the mold will be described. The flow of this analysis is exactly the same as the flowchart (FIG. 2) showing the procedure of the structural analysis processing in the first embodiment.
[0089]
Therefore, here, the PVT state of the resin is calculated from the temperature determined in each step of the thermal structure coupled analysis and the hydrostatic pressure calculated from the stress value using the flowchart showing the heat shrinkage strain calculation processing procedure shown in FIG. The means for calculating the specific volume by the equation and the specific means for calculating the linear expansion coefficient from the obtained specific volume and calculating the thermal strain increment in the next step will be described in detail.
[0090]
By executing the flow analysis shown in step S3 in FIG. 1, the structural analysis input data such as element node data, boundary conditions, and analysis control data are read (step S20), and the temperature and pressure analysis results have already been created by the flow analysis. Therefore, these data are input as initial values (step S21), and the structural analysis (S6) is started.
[0091]
First, the pressure data P0 read as the flow analysis result
Based on the temperature data T0, the specific volume V0 is calculated by the PVT equation of state (steps S31 and S32 in FIG. 26). In the processing of FIG. 26, the element number n and the time t are set to a value 0 as initial values (step S30). As the PVT state equation of the resin, a Spencer-Gillmore equation represented by the equation (3) or a Tait equation represented by the equation (4) is generally used.
[0092]
V (T, P) = (Z (P + W) + RT) / (P + W) (3)
Here, W: constant, R: constant, and Z: constant.
[0093]
V (T, P) = Z (T) [1−C · ln (1 + P / B (T)) (4)
Here, B (T): pressure dependent constant, C: constant, Z (T): constant
Next, when the temperature Tn at an arbitrary position of the molded article is obtained for each analysis time interval Δt (steps S33 and S34), a specific volume Vn at time t = t + Δt is obtained from the PVT equation of state (step S35). FIG. 27 is a graph showing the relationship between specific volume, temperature, and pressure calculated from the PVT equation of state. However, at this time, the pressure P in the PVT equation of state is the pressure P0 read as an initial value from the flow analysis result.
It is.
[0094]
Assuming that the resin isotropically contracts, the linear expansion coefficient αn is calculated from the specific volume (Vn−V0) at the time step Δt and the temperature change ΔT according to the equation (5) (step S36).
[0095]
αn = ((Vn / V0) 1 / 3−1) / ΔT (5)
Since the heat shrinkage strain ΔeV with respect to the temperature change ΔT in the first step of the analysis is obtained from this αn (step S37), the viscoelastic analysis in consideration of the mold constraint in steps S22 and S23 is performed to reduce the stress distribution. It is determined (step S38).
[0096]
In addition, it has been confirmed by the applicant's past experiments that thin-walled molded articles and the like exhibit anisotropic shrinkage behavior in the flow direction (in-plane direction) and the sheet thickness direction. The method of handling this anisotropic shrinkage is already disclosed in JP-A-7-186228 and JP-A-8-23008, and the anisotropic shrinkage strain ΔεP can be calculated by equation (6). .
[0097]
ΔεZ = A + B · ΔeV
ΔεP = (ΔeV−ΔεZ) / 2 (6)
Here, ΔεZ: contraction rate in the thickness direction, ΔεP: contraction rate in the in-plane direction, A, B: contraction coefficient, ΔeV: volume contraction rate
Here, based on the specific volume obtained from the PVT equation of state, the linear expansion coefficient or the heat shrinkage strain is obtained, and the conventional structural analysis method for obtaining the shape accuracy of the plastic molded article is based on the thermal deformation temperature during the filling, holding and cooling process. This is a method of performing linear elasticity analysis (thermal stress analysis) by calculating a pressure temperature distribution at a shrinkage starting point such as a solidification temperature or a flow stop temperature and a linear expansion coefficient or a heat shrinkage strain between room temperature and normal pressure. . Therefore, no consideration is given to the dependence on the load path (time) such as stress relaxation and creep caused by the mold restraint of the molded product from the shrinkage starting point to room temperature.
[0098]
In the present embodiment, the process of cooling the mold and the entire molded article is performed by an unsteady temperature analysis (Step S22) and a structural analysis (Step S23) in consideration of viscoelasticity that can consider load path (time) dependence. We will ask for it by implementing it. At this time, the temperature Tn at an arbitrary position of the molded article is set at every time interval Δt
, Pressure (hydrostatic pressure) Pn, specific volume Vn is calculated from the PVT equation of state shown in step S35, and heat shrinkage strain Δε is obtained.
[0099]
As described above, the specific method of the structural analysis (S23) in which the viscoelasticity is considered is, as described above, a material which is considered to be a thermorheologically simple material to which the time-temperature conversion rule can be applied. Then, a linear viscoelastic model that is approximated by a master curve using a Prony series for the relaxation elastic modulus is applied.
[0100]
In the present invention, the dynamic viscoelastic characteristic obtained in each of the solidified state and the molten state of the resin is one as described in the first embodiment, instead of the viscoelastic master curve obtained in the solidified state of the resin. A viscoelastic master curve integrated with the above is created, and the above-mentioned equations (1) and (2) are applied to the relaxation elastic coefficient and the shift function, respectively, and used.
[0101]
Next, as a method for more accurately handling the influence of the mold constraint on the surface of the molded product and the surface of the mold, in the first embodiment described above, after completing the structural analysis (S23) in consideration of the viscoelasticity of each step, the molding is performed. A contact / dissociation determination is performed on the product surface and the mold surface based on the contact distance between them (the distance between element nodes constituting the contact surfaces of both the molded product and the mold) and the reaction force at the contact surface constituting nodes (step S24). An analysis method in which the heat transfer rate is set on the contact surface between the molded product and the mold when contact is determined, and the thermal conductivity is set between the molded product surface and the cavity space when dissociation is determined and reflected in the temperature analysis in the next step Was shown. However, this method may be a problem that is very strong in nonlinearity analytically, there is a problem that stable analysis results are not obtained depending on the analysis model shape, or the calculation cost is very high, Not efficient.
[0102]
Therefore, in the present embodiment, it is considered that the influence of factors such as contact friction, slip, and dissociation between the molded product and the mold on the deformation of the molded product is small within a range of molding conditions in which a normal proper molded product is obtained. The influence of the deformation of the mold due to the pressure at the time of holding pressure and the effect of the mold constraint on the surface of the mold and the surface of the mold due to cooling and solidification are considered as an integrated model having no contact behavior between the molded article and the mold.
[0103]
Specifically, it is assumed that both are completely adhered (fixed) on the surface of the molded product and the surface of the die until the molded product is removed from the mold at a temperature at which the molded product can be removed (release temperature). Is omitted.
[0104]
Then, after the molded product is taken out (mold release), the mold part of the analysis model is deleted, and a viscoelastic stress analysis is performed only on the molded product, and the mold restraint is released immediately after the mold release. The amount of springback deformation and the thermal conductivity between the surface of the molded product and the cavity space are set, and the amount of thermal deformation until the temperature of the molded product finally reaches room temperature is analyzed.
[0105]
The procedure of the above-mentioned unsteady temperature analysis (S22) and the structural analysis (S23) in consideration of the viscoelasticity are repeated until the molded product taking-out temperature or time inputted as the molding condition is reached (step S25). Note that the contact / dissociation determination in step 24 is omitted in the present embodiment. Then, at the time of the removal condition, the mold release processing (the molded product is released from the constraint by the mold) is performed. However, as described above, the mold and the molded product are analyzed as a continuous integrated model on the analysis model. Therefore, the Spring Bck amount at the time of mold release of the molded product is calculated by excluding only the mold portion from non-rigidity as an object to be analyzed later (step S26).
[0106]
After that, the heat conduction conditions between the molded product and the mold, which were analyzed so far, were changed to heat transfer boundary conditions from the molded product to the atmosphere. Until the molded product reaches room temperature, the calculation is performed by repeating the unsteady temperature analysis (step S26A) and the structural analysis considering the viscoelasticity (step S26B) (step S26C), and finally the deformation amount, stress, strain, etc. The calculation result is output (step S27).
[0107]
[Example 2]
FIG. 28 is a view showing the shape of a molded product.
[0108]
As shown in FIG. 28, the above analysis procedure is based on a toric lens shape having an optical surface shape having a radius R1 = 259.2 mm and a radius R2 = 156.12 mm in a rectangular shape having an outer length of 102 mm and a width of 11.6 mm. The case where the amount of deformation (bending amount) in the generatrix direction (lens longitudinal direction) of the optical surface is obtained by analysis is shown. The flow of the entire analysis proceeds according to the analysis procedure of FIGS. 1 and 26 already described in detail.
[0109]
FIG. 29 is a diagram showing a whole mold model including a lens-shaped mold. However, since it is symmetrical in the longitudinal direction at the center of the lens width, it is a 1/2 model. The entire mold model is a model including a mold and a molded product on each of the fixed side and the movable side.
[0110]
Then, as shown in FIG. 30, the entire model is divided into about 7000 elements by the element division preprocessor, and various boundary conditions such as a symmetry plane, a material area of a mold and a molded product, and an inflow boundary are defined. Create input data for flow analysis. FIG. 30 is a diagram showing the entire analysis model obtained by element division. FIG. 31 is a diagram showing only a molded product part obtained by element division. It should be noted that boundary conditions for structural analysis such as constraint conditions to be performed after the flow analysis are also added. The molding conditions used in the analysis are as follows.
[0111]
・ Resin used Polyolefin resin
・ Resin temperature 270 ℃
・ Filling time 0 sec
・ Mold temperature 120 ℃ (constant)
・ Holding pressure setting value 1060kgf / cm2 (actual value in the mold 848kgf / cm2)
・ Holding time 30sec
・ Cooling time 120sec
First, the process of filling the resin into the mold and holding and cooling is performed by flow analysis, but in order to consider the heat transfer between the molded product and the mold, the entire process from filling to holding and cooling is performed. Transient heat conduction analysis is also performed at the same time. As the analysis program, commercially available general-purpose fluid analysis software is used, and the viscosity is a non-Newtonian property of the resin which depends on the temperature and the shear rate. The viscosity equation based on the power law and the Spencer-Gillmore PVT equation of state, which is the relational expression of pressure, temperature, and specific volume required during packing analysis, as shown in the above-mentioned equation (3), are attached to the software. Define using a user subroutine.
[0112]
μ = A · γB · exp (C · T) (7)
Here, A, B, and C are constants determined by the resin.
[0113]
V (T, P) = (Z0 (P + W) + RT) / (P + W) (3)
Here, W: constant, R: constant, and Z0: constant.
[0114]
At the same time, by incorporating a data conversion program that creates the structural analysis input data to be executed immediately after the flow analysis using this user subroutine, the pressure, temperature data, shape, Ensure that input data is created.
[0115]
FIG. 32 is a diagram showing the progress of the melt front at the time of filling analysis obtained in the present analysis. FIG. 33 is a diagram showing a pressure distribution after the start of holding pressure. FIG. 34 is a diagram showing the temperature distribution of the molded product at the time when the flow of the resin is stopped during the pressure-holding cooling process (in the present analysis example, after 20 seconds from the start of the pressure-holding).
[0116]
Next, the analysis of the heat shrinkage behavior during cooling of the molded product after the holding pressure cooling process was completed, using the element division model used at the time of flow analysis as it was, at the time when the flow of resin during flow analysis stopped. The final results of temperature and pressure are taken into the structural analysis as initial data.
[0117]
FIG. 35 is a diagram showing the temperature distribution of the entire mold and molded product at the time when the flow of the resin is stopped. FIG. 36 is a diagram showing a temperature distribution of a molded product part. FIG. 37 is a diagram showing the pressure distribution after the pressure distribution in the flow analysis is converted into the initial stress (compression stress) in the structural analysis.
[0118]
Until the mold release, the unsteady temperature analysis between the molded product and the mold and the structural analysis taking into account the mold constraint will be performed while being coupled with the thermal analysis. In this analysis, both the mold and the molded product are analyzed as a deformed body, but the molded product is subjected to thermal stress analysis in consideration of viscoelasticity.
[0119]
At this time, in the original analysis, the interface between the mold and the molded product is considered as a contact analysis problem, and the effects of mold constraints such as contact and dissociation between the surface of the molded product and the surface of the mold due to cooling and solidification are considered. This means that, for example, the heat transfer coefficient between the molded product and the mold is set at the time of contact determination, and the heat transfer coefficient is set such that the space between the molded product surface and the cavity space is insulated during the dissociation determination, and the analysis proceeds. It is desirable. However, under the proper molding conditions under which normal good products can be obtained, the interface between the mold and the molded product is fixed (adhered) until the mold is released, and it is considered that dissociation between the mold and the molded product does not occur. In this analysis, the calculation is simplified by excluding the contact analysis and assuming that the mold and the molded product are integrated until the release. As a result, the analysis time is shortened, and there is a merit of improving the efficiency of the analysis work.
[0120]
The analysis program uses a commercially available general-purpose nonlinear structural analysis program, and considers the resin molded part as a thermorheologically simple material to which the time-temperature conversion rule can be applied. An analysis is performed by defining a linear viscoelastic constitutive equation (Equation (1)) and a shift function (Equation (2)) that can approximate a relaxation function using analysis input data and a user subroutine.
[0121]
On the other hand, in this process, at the same time, the temperature and pressure (hydrostatic pressure) at an arbitrary position of the molded article at each time interval are obtained, the specific volume is obtained from the above-mentioned PVT equation of state (Equation (3)), and the heat shrinkage strain is obtained. By calculating, analysis is performed taking into account the effect of pressure (hydrostatic pressure). Note that the viscoelastic properties used in this analysis are the same as those of the polyolefin-based resin described in the first embodiment. Since the analysis input data has already been created at the time of executing the flow analysis, it is possible to immediately execute the structural analysis. The above calculations are performed until the mold release time, which is the molded product removal time (in this analysis, the cooling time is 120 seconds).
[0122]
At the time of release, the mold release process (the molded product is released from the constraint by the mold) is performed. However, as described above, the mold and the molded product are analyzed as a continuous integrated model on the analytical model. Therefore, in the present embodiment, the spring back amount at the time of mold release of the molded product is calculated by excluding only the mold portion from the analysis target as having no rigidity.
[0123]
After that, the heat conduction conditions between the molded product and the mold that were analyzed so far were changed to the heat conduction boundary condition from the molded product to the atmosphere, and the free shrinkage behavior accompanying the natural cooling in the air was continued for the molded product. By repeating the unsteady temperature analysis and the structural analysis taking viscoelasticity into consideration until the room temperature is reached, the calculation is further advanced, and the final calculation results of the amount of deformation, stress, strain, etc. are output.
[0124]
FIG. 38 shows that, at the node numbers 575, 638, and 701 in the center of the lens molded product, the cooling state under the constraint of the mold at the start of the analysis, the mold release time, and the natural cooling in the air reach room temperature. It is a figure which shows the temperature history up to.
[0125]
FIG. 39 is a diagram comparing the deformed state of the R1 optical surface and the R2 optical surface of the lens molded product in the generatrix direction at the time when the molded product is taken out of the mold and reaches room temperature by actual measurement values and analysis values. On the R1 optical surface, the amount of deformation of the lens molded product is about 16 μm, whereas the analysis value is 25 μm, and on the R2 optical surface, the analysis value is about 40 μm, but the analysis value is 15 μm. is there.
[0126]
FIG. 40 is a view showing the result of similarly verifying the bending amount in the generatrix direction for other plural lens components (four components A, B, C, and D). Lens parts A and B shown in the figure are long toric lenses having a lens length of about 260 mm and 240 mm, respectively, and lens parts C and D are toric lenses having a lens length of about 90 mm and 50 mm, respectively. The bending amount in the generatrix direction in the figure is shown by comparing an actually measured value and an analysis value within the lens effective range.
[0127]
Further, FIG. 41 is a diagram showing the results of comparative verification of the shape profiles of the lens component (D component) with respect to the bending in the generatrix direction (R1 surface), and both are in good agreement. Finally, FIG. 42 is a diagram showing a result of shape verification performed in the sagittal direction R for each of the R1 and R2 surfaces on the gate side, the lens center, and the opposite side to the gate of the lens component (C component).
[0128]
Both the R1 surface and the R2 surface result in a smaller radius r after molding than the initial design value R, indicating that the tendency can be calculated in the analysis. Further, the Newton error in the figure is a value obtained by converting the maximum deviation in the range of the optically effective width d in the sagittal direction as the number of Newtons for r after molding with respect to the design value R. Good agreement.
[0129]
In this way, the deformation amount of the lens molded product can be predicted almost quantitatively by the present analysis method, and by referring to the actual measurement values of similar lens components in the past, the initial correction of the deformation amount in advance can be performed. A mold can be created, and the cost and cost of mold production can be significantly reduced.
[0130]
The simulation apparatus for the injection molding process according to the present embodiment has been described above. The simulation apparatus for the injection molding process for performing the analysis processing described in each embodiment includes, for example, a well-known CPU, ROM, RAM, and I / O. It can be composed of a computer system such as a computer main body having an interface, a keyboard, a CRT display, an external memory, and a printer. The CPU executes various program modules stored in the external memory, so that the shape definition unit 1, Each function of the flow analysis unit 2 and the structure analysis unit 3 is specifically realized.
[0131]
【The invention's effect】
As apparent from the above description, according to the present invention, the final molded product shape can be accurately predicted in consideration of the viscoelastic properties of the resin such as stress relaxation and creep. In addition, the final molded product shape can be accurately predicted in consideration of the viscoelastic properties such as stress relaxation and creep of the resin, and the effects of mold constraints at the contact surface between the molded product and the mold. .
[0132]
In addition, taking into account the effects of temperature and pressure factors during molding, the effects of the viscoelastic properties of the resin, the heat transfer between the molded product and the mold, and the effects of mold constraints at the contact surface are also considered at the same time. Shape accuracy can be obtained with higher accuracy.
[0133]
Furthermore, since it is possible to study before manufacturing a mold using a computer, it is possible to shorten the study time until determining the optimal shape, and to reduce the cost of mold manufacture and modification. Can be.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an overall analysis processing procedure in an injection molding process simulation apparatus.
FIG. 2 is a flowchart showing a structural analysis processing procedure in consideration of a viscoelastic characteristic of a resin and a mold constraint such as a contact state between the resin and the mold at the time of cooling in the mold and a mold release state in step S6. is there.
FIG. 3 is a diagram schematically illustrating an apparatus for measuring dynamic viscoelasticity by a forced torsion method using a rectangular test piece.
FIG. 4 is a view schematically showing an apparatus for measuring dynamic viscoelasticity by a shear method using a disk test piece.
FIG. 5 is a graph showing a measurement result of an angular frequency dependence of a storage elastic modulus G ′ obtained by a dynamic viscoelasticity measurement by a torsional method at each temperature from a solid region to a melting transition region.
FIG. 6 is a graph showing a measurement result of angular frequency dependence of a loss elastic modulus G ″ obtained by a dynamic viscoelasticity measurement by a torsional method at each temperature from a solid region to a melting transition region.
FIG. 7 is a graph showing a measurement result of an angular frequency dependence of a storage elastic modulus G ′ obtained by a dynamic viscoelasticity measurement by a shear method at each temperature from a melting transition region to a melting region.
FIG. 8 is a graph showing a measurement result of an angular frequency dependence of a loss elastic modulus G ″ obtained by a dynamic viscoelasticity measurement by a shear method at each temperature from a melting transition region to a melting region.
9 is a graph showing the frequency dependence of the storage elastic modulus after shifting and superposing the storage elastic modulus G ′ at each temperature obtained by the dynamic viscoelasticity measurement by the torsion method of FIG. 5;
10 is a graph showing the frequency dependence of the loss elastic modulus after shifting and superimposing the loss elastic modulus G ″ at each temperature obtained by the dynamic viscoelasticity measurement by the torsional method of FIG. 6;
11 is a graph showing the frequency dependence of the storage modulus after superimposing the storage modulus G 'at each temperature obtained by the dynamic viscoelasticity measurement by the shear method of FIG. 7;
12 is a graph showing the frequency dependence of the loss elastic modulus after superimposing the loss elastic modulus G ″ at each temperature obtained by the dynamic viscoelasticity measurement by the shear method in FIG.
FIG. 13 is a graph showing temperature dependence of a shift factor (shift factor) shifted at the time of superposition in FIGS. 9 and 10;
FIG. 14 is a graph showing temperature dependence of a shift factor (shift factor) shifted at the time of superposition in FIGS. 11 and 12;
FIG. 15 is a graph showing a master curve relating to the time dependence of the storage elastic modulus G ′ and the loss elastic modulus G ″ obtained by superposing the results obtained by the shearing method on the reference temperature of 138 ° C. by the torsion method.
FIG. 16 is a graph showing the temperature dependence of a transfer factor (logaT) when FIGS. 13 and 14 are further superimposed.
FIG. 17 is a graph showing the relationship between the relaxation elastic coefficient G (t) and the temperature obtained by converting the storage elastic modulus G ′ and the loss elastic modulus G ″ obtained from FIG. It is.
FIG. 18 is a graph in which the time-temperature transfer factor obtained from FIG. 16 is approximated by a polynomial shown in Expression (2), and the two are compared.
FIG. 19 is a view showing a specific molded product shape.
20 is a diagram showing the shape of the entire die model including the thick flat plate of FIG. 19;
FIG. 21 is a diagram showing a whole mold model divided into 5000 elements.
FIG. 22 is a diagram showing a temperature distribution of a molded product at the time when the dwelling cooling process obtained by the flow analysis is completed (when the flow of the resin is stopped).
FIG. 23 is a diagram showing a temperature distribution of a whole mold model.
FIG. 24: Molding in which the temperature is high due to heat insulation at the surface of the molded product (resin inlet side) where the molded product is dissociated from the mold in the cavity due to the volume contraction of the resin due to cooling, and the molding is in contact with the mold. It is a figure which shows the example which has produced the temperature fall in the product surface part.
FIG. 25 is a view showing deformation of a molded product at the time when the molded product is taken out of the mold obtained in the present analysis.
FIG. 26 is a flowchart showing a procedure for calculating a heat shrinkage strain.
FIG. 27 is a graph showing the relationship between specific volume, temperature, and pressure calculated from the PVT equation of state.
FIG. 28 is a view showing a shape of a molded product.
FIG. 29 is a diagram showing an entire mold model including a lens-shaped mold.
FIG. 30 is a diagram showing an entire analysis model obtained by dividing elements.
FIG. 31 is a diagram showing only a molded product part obtained by dividing the element.
FIG. 32 is a diagram showing the progress of the melt front at the time of filling analysis obtained in the present analysis.
FIG. 33 is a diagram showing a pressure distribution after the start of holding pressure.
FIG. 34 is a diagram showing a temperature distribution of a molded product at the time when the flow of the resin is stopped during the pressure-holding cooling process (in this analysis example, 20 seconds after the start of the pressure-holding).
FIG. 35 is a diagram showing the temperature distribution of the entire mold and molded product at the time when the flow of the resin is stopped.
FIG. 36 is a diagram showing a temperature distribution of a molded product part.
FIG. 37 is a diagram showing a pressure distribution after converting a pressure distribution in a flow analysis into an initial stress (compression stress) in a structural analysis.
38. At node numbers 575, 638, and 701 at the center of the lens molded product, the temperature reaches room temperature by natural cooling in the atmosphere from the cooling state under the constraint of the mold at the start of the analysis, after the mold release time. It is a figure which shows the temperature history up to.
FIG. 39 is a diagram comparing the measured state and the analyzed value of the deformation state of the R1 optical surface and the R2 optical surface of the lens molded product in the generatrix direction when the molded product is taken out of the mold and reaches room temperature.
FIG. 40 is a diagram showing a result of verifying a bending amount in a generatrix direction of various lens components (four components of A, B, C, and D).
FIG. 41 is a diagram showing the result of verifying the shape profile of the bending in the generatrix direction (R1 surface) of the lens component (D component).
FIG. 42 is a diagram showing the results of shape verification performed in the sagittal direction R for each of the R1 and R2 surfaces on the gate side, the lens center, and the opposite side of the lens in the lens component (C component).
[Explanation of symbols]
1 Shape definition part
2 Flow analysis section
3 Structural Analysis Department
11 Mold whole model
11a Fixed side mold
11b Movable mold
11c Molded product

Claims (8)

Heat transfer analysis means for performing heat transfer analysis of molds and molded products, flow analysis means for performing thermo-fluid analysis of filling pressure holding cooling behavior of molten resin in molds, and structural analysis of molded products and molds An injection molding process simulation device comprising a structural analysis means and predicting the shape accuracy of a molded product,
The heat transfer analysis of the mold and the molded product, and the pressure and temperature calculating means for calculating the temperature of the mold and the pressure and temperature of the molded product by performing the thermal fluid analysis of the molded product alone or in combination, Structural analysis means, with the calculated pressure and temperature as initial values, performing a structural analysis taking into account the viscoelastic properties of the resin and the resin, the mold and the molded product simultaneously considering the mold and the molded product, An injection molding process simulation apparatus, which calculates the shape accuracy of a molded article deformed due to heat shrinkage. In the shape accuracy prediction method for predicting the shape accuracy of a molded product,
A step of calculating the temperature of the mold and the pressure and temperature of the molded article by performing the heat transfer analysis of the mold and the molded article, and the thermal fluid analysis of the molded article alone or in combination, and calculating the calculated pressure and With the temperature as the initial value, the mold and the molded product are considered at the same time, and the mold analysis between the mold and the molded product and the viscoelastic properties of the resin are performed. Calculating a precision. Heat transfer analysis means for performing heat transfer analysis of molds and molded products, flow analysis means for performing thermo-fluid analysis of filling pressure holding cooling behavior of molten resin in molds, and structural analysis of molded products and molds An injection molding process simulation device comprising a structural analysis means and predicting the shape accuracy of a molded product,
A pressure / temperature calculating means for performing the heat transfer analysis of the mold and the molded product and the thermal fluid analysis of the molded product individually or in combination to calculate the temperature of the mold and the pressure and temperature of the molded product. The structural analysis means may combine the calculated pressure and temperature as initial conditions into viscoelastic properties obtained in a solidified state of the resin, or viscoelastic properties obtained from each of a solidified state and a molten state of the resin into one. Injection molding process simulation characterized by creating an integrated viscoelastic property and performing a structural analysis to determine a deformation behavior of a mold and a molded article due to thermal shrinkage using the created viscoelastic property. apparatus. In the shape accuracy prediction method for predicting the shape accuracy of a molded product,
A step of calculating the temperature of the mold and the pressure and temperature of the molded article by performing the heat transfer analysis of the mold and the molded article, and the thermal fluid analysis of the molded article alone or in combination, and calculating the calculated pressure and Viscoelastic properties obtained in the solidified state of the resin with temperature as the initial condition, or viscoelastic properties obtained by integrating the viscoelastic properties obtained from each of the solidified state and the molten state of the resin into one are created and the created Performing a structural analysis to determine the deformation behavior of the mold and the molded product due to thermal shrinkage using the viscoelastic characteristics. Heat transfer analysis means for performing heat transfer analysis of molds and molded products, flow analysis means for performing thermo-fluid analysis of filling pressure holding cooling behavior of molten resin in molds, and structural analysis of molded products and molds An injection molding process simulation device comprising a structural analysis means and predicting the shape accuracy of a molded product,
The heat transfer analysis of the mold and the molded product and the thermal fluid analysis of the molded product are performed alone or in combination with each other, and a pressure / temperature calculating unit is provided for calculating the temperature of the mold and the pressure and temperature of the molded product, When performing structural analysis of the mold and the molded article using the calculated pressure and temperature as initial conditions, the structural analysis unit has a contact friction behavior between the mold and the molded article until immediately before release. In the case of, or in the case of complete close contact, the calculation means taking into account the mold constraint in either case, and after the release, the mold part is deleted and the only the molded product is calculated as a model An injection molding process simulation apparatus, comprising: a calculating means after release from the mold; and calculating a deformed shape accuracy accompanying thermal shrinkage of the molded product at the time of release. In the shape accuracy prediction method for predicting the shape accuracy of a molded product,
Performing a heat transfer analysis of a mold and a molded article and a thermal fluid analysis of the molded article alone or in combination, and calculating the temperature of the mold and the pressure and temperature of the molded article; and the calculated pressure. When performing the structural analysis of the mold and the molded product with the temperature and temperature as the initial conditions, whether there is a contact frictional behavior between the mold and the molded product or immediately before the mold is released, until just before the mold release. A step of calculating taking into account the mold constraint, and a step of removing the mold part after demolding, and calculating using only the molded article as a model. A shape accuracy prediction method characterized by calculating a deformed shape accuracy accompanying shrinkage. Heat transfer analysis means for performing heat transfer analysis of molds and molded products, flow analysis means for performing thermo-fluid analysis of filling pressure holding cooling behavior of molten resin in molds, and structural analysis of molded products and molds An injection molding process simulation device comprising a structural analysis means and predicting the shape accuracy of a molded product,
The heat transfer analysis of the mold and the molded product, and the pressure and temperature of the molded product is calculated by performing the thermal fluid analysis of the molded product alone or in combination, and calculating the temperature of the mold and the pressure and temperature of the molded product. The structural analysis means performs a structural analysis in consideration of the viscoelastic properties of the resin based on the calculated pressure and temperature, and obtains a specific volume from a temperature and an average stress value (hydrostatic pressure) obtained from the structural analysis by a state equation of the resin. Injection molding process simulation apparatus, comprising: a specific volume calculating means for calculating a specific shrinkage; and a heat shrinkage strain calculating means for calculating an isotropic or anisotropic heat shrinkage strain from the calculated specific volume. . In the shape accuracy prediction method for predicting the shape accuracy of a molded product,
The heat transfer analysis of the mold and the molded product, and the pressure and temperature of the molded product is calculated by performing the thermal fluid analysis of the molded product alone or in combination, and calculating the temperature of the mold and the pressure and temperature of the molded product. The structural analysis means performs a structural analysis in consideration of the viscoelastic properties of the resin based on the calculated pressure and temperature, and obtains a specific volume from a temperature and an average stress value (hydrostatic pressure) obtained from the structural analysis by a state equation of the resin. And a heat shrinkage strain calculation means for calculating an isotropic or anisotropic heat shrinkage strain from the calculated specific volume, thereby obtaining the deformation shape accuracy accompanying the heat shrinkage of the molded article. A shape accuracy prediction method characterized by calculating.

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